Aquamarine Pictures
by Mark
Stunning Aquamarine pictures
Aquamarine Pictures
Chelsea Filter
Chelsea Filter
by Ritika Changrani
Also known as Emerald filter, Chelsea filter is used to identify natural, synthetic and imitated gemstones. Developed by the British Gemmologists Anderson and Payne, this filter was initially developed only for the separation of natural emerald from green beryl. Now it is being used to identify various gemstones.
Chelsea Filter – Gemstone Testing Tool
Chelsea filters are designed to absorb all lights except red and yellow green which are transmitted through the filter. This causes different gemstones to exhibit different colors when observed through the Chelsea filter. Emeralds, when seen through the filter, appear red or pink in colour, while ruby appears brilliant red. Synthetic blue spinals appear yellowish orange or pink while the gems which are imitations appear green or greenish grey. Cobalt glass imitations of sapphire appear deep red.
How to use a Chelsea Filter
Hold the Chelsea filter close to the eye – may be at a distance of an inch or two from your eye. Provide strong light to the gemstone by lighting with a torch or bulb. Hold the torch or bulb such that the light falls directly down on the stone. When viewed from the filter, the stone may appear to change its colour. Never hold the Chelsea filter close to the stone since it may produce wrong results.
How does a Chelsea Filter Work?
Chelsea Filter works based on the characteristics of the gemstone. The Chelsea filter detects the presence of chromium and cobalt in the gemstone. Chromium, if present in the gemstone, produces red and green colour as in ruby and emerald, and the presence of cobalt gives a blue colour. It is the amount of chromium or cobalt present which gives a dark or light colour.
When white light is passed through a gemstone, it absorbs colours of some wavelength and lets other colours free. The other colours which are not absorbed by the Chelsea filter mix up and give the colour appearance to the eyes. Depending on the appearance of the colour when viewed through the Chelsea filter, it is easy to detect the type of gemstone it is. For example, when white light is passed through the Emerald, emerald absorbs all the yellow-green wavelengths. Chelsea colour filter can filter all the colours except yellow-green and deep red wavelengths. Since yellow-green wavelength is already absorbed, only the red colour passes through the Chelsea filter.
One has to make sure that there is enough light on the stone, else the reaction may not be visible to the eye.
Gemstones identified by Chelsea Filter
Red Stones
Red stones that contain chromium are Burma ruby, synthetic ruby and red spinel. Ruby and spinel when viewed through the Chelsea filter appear red. Demantoid Garnet when examined through the Chelsea filter in presence of light appears pinkish. Though Thai ruby and pyrope garnet contain chromium, there is no colour change observed due to the presence of iron in those stones, which prevents colour change. Red stones like garnets and paste do not contain chromium and hence there is no colour change. When viewed through the Chelsea filter, they appear dark red or black in colour.
Therefore when you are examining a group of red stones, you can easily separate different kinds of gemstones. Those which impart brilliant red are synthetic rubies. Stones which glow slightly red are natural rubies and spinals. Thai and Demantoid garnet may turn pinkish or slightly red. The stones which remain dark red or black are paste and other garnets.
Green Stones
Beryl is a green coloured stone which is coloured by chromium. The different types of beryl are emerald and aquamarine. Natural emeralds have a smaller amount of chromium, while synthetic emeralds have larger amount. Hence the change in natural emeralds is to dull or a little bright red. Synthetic emeralds change their colour to bright red. Some synthetic emeralds produce a dull red colour due to the presence of iron. Some natural emeralds like South African and Indian emeralds do not produce any red glow when viewed through the Chelsea filter. Chelsea filter can just give an idea that the gemstone may or may not be an emerald but the test is not a proof of detecting an emerald.
Some stones can be confused with the emerald. They are Demantoid garnet, green garnets or savolite and tourmaline. All these stones when tested using the Chelsea filter, appear to glow red and are often mistaken to be emeralds.
Green gemstones can be distinguished from each other by some of their characteristics. Emeralds produce an oily luster when seen through a Chelsea filter. Green garnets appear brighter than emeralds. Green zircon appears pinkish in colour and exhibits double refraction. Tourmaline is also a stone which exhibits double refraction. When green zircon and tourmaline are viewed through a 10X lens, the back faces of the stones appear to be doubled. Aquamarine has iron content due to which the colour produced is dull. The colour change in aquamarine is from blue-green to muddy grey-green. Green garnet, green zircon and chalcedony show very little colour change and appear pink or red. Pastes, green sapphire and peridot appear remain dark-green. Alexandrite appears red when seen through the Chelsea filter.
Blue stones
Blue stones contain cobalt which can be detected by the Chelsea filter. The colour change of blue stones when viewed though the Chelsea filter is red in highly doped stones and orange brown or green in light blue stones. The colour change to red when viewed though the Chelsea filter is an indication that the gem stone is synthetic. Sapphires show no colour change and remain dark blue or black.
How to take Care of a Chelsea filter
- It is recommended not to touch the Chelsea filter as it may leave marks on the glass. A soft dry cloth must be used to remove the dust.
- Never put the Chelsea filter in water or any liquid.
- The Chelsea filter must not be allowed to get heated either in direct sunlight or on a radiator.
- When not in use, the Chelsea filter must be kept closed.
Chelsea filter is an important tool in the field of gemology which can be used to test various stones. Although, the test is not cent percent reliable since the composition of every gemstone is not the same even in the similar type of stones, it is used by a number of gem testers for testing the gemstones.
More Info: Gem Testing Tools
HOW TO BUY AN ENGAGEMENT RING
by Reuben Robert
It doesn’t always need to be a diamond. It’s true. Many feel the modern tradition of diamonds is over-sold. Remember that the value of the engagement ring will mean different things to different women.
So you’ve decided to pop the question and the next thing in order is an Engagement Ring, to commemorate your eternal commitment to the one you love. Of course, the debate still rages: Why do we need to buy a ring? Is the expense worth all the hype? Does it mean anything at all? When did all this begin, anyway?! Well, the following trivia may help:
* Egyptians believed that the “love vein” (vena amoris) ran straight from the fourth finger to the heart.
* Judeo-Christian ethos considers the ring’s significance as its symbol of everlasting continuity.
* Most agree the tradition of buying a diamond engagement ring began in 1477, when Archduke Maximillian of Austria bought his future wife Mary of Burgundy a large diamond.
* Still more believe it’s a vast conspiracy on the part of the jewelry industry to rake in all our money! Just remember, in matters of the heart, one needs little justification for any act, senseless or otherwise. Follow your heart, and let it decide what you want.
1. YOUR BUDGET – FOLLOW YOUR HEAD, NOT YOUR HEART!
I know I’ve just contradicted myself, but hey, this is an important point. It’s all very well that you’ve decided to go in for the ring, however here’s the guideline: Jewelry is expensive. Good jewelry is even more expensive. Great jewelry is… But you get the point. Solicit ideas may be a good idea. Speak to men who’ve already done the deed. A family member could have some advice. Your local jeweler will simply be bursting with ideas too. However, ensure that the final decision is yours. Nothing else will do. Here are some tips to help you along. It doesn’t always need to be a diamond. It’s true. Many feel the modern tradition of diamonds is over-sold. Remember that the value of the engagement ring will mean different things to different women. Most women believe more in the symbolic value of the ring, especially if the proposal is sincere. There are many imitation diamonds in the market, but remember that while it may fool some, it will never fool her. My advice, don’t even try. But do take heart; there are many alternatives to diamonds that are affordable, romantic and of symbolic value too.
A Ruby or a Red Garnet symbolizes the passion and zest for life, and everything the heart stands for. Other marginally more expensive alternatives are the Red Tourmaline or Red Spinel. Choices in green include the Green Garnet and Green Tourmaline, and the enchanting Emerald, all of which stand for the everlasting symbols of faithfulness and continuity. The Blue Spinel, Iolite, Blue Tourmaline and Sapphire stand for purity and spirituality. The Pearl has long been associated with love and weddings, far before any other gemstone. Try and find a natural pearl in an heirloom or antique piece. A good idea would be to combine the stone of your choice with a small diamond on either side to complete the symbolism with the aura of indestructibility and infinity that the diamond stands for. An important thing is to decide whether she prefers her birthstone itself. It will make it more personal, closer to her heart.
So no matter what your budget, and no matter what you want to say, these beautiful, rare and precious choices are well within reach. It simply has to incorporate the correct symbolism for the two of you, while showing thoughtfulness and caring. However, society sometimes fuels unrealistic expectations for the perfect engagement ring, and you may decide to go in for a diamond ring after all. Or maybe, you can actually afford one quite easily. Whatever the reason, remember to separate yourself from the benchmarks that others set, and make this decision based on your own preference. Most financiers and jewelers agree that an ideal budget would be in the range of approximately 2 or 3 months’ salary. Some choose to spend more because they have another disposable income, and many find a good ring spending less than the prescribed budget. Just remember, matters of the heart are generally directly disproportionate to your bank balance! Use your head, that’s all.
2. WHAT DOES THE LOVE OF YOUR LIFE ACTUALLY LIKE?
You will now have to begin doing things that most men find very difficult. Start Paying Attention!
* What is the metal color she prefers? Unlike men, most women will have a definite preference. Your choices will vary between White gold, Yellow gold, Rose gold or Platinum.
* Does she now wear jewelry that is vintage or antique? Or does her preference lean towards modern contemporary design, or is she prejudiced to classic and timeless designs that never go out of fashion?
* Her regular jewelry is probably the best indication of her taste, especially because it almost surely is made up of items she is most comfortable with. Are You Listening?
* If she’s ever mentioned an opinion, it’s a definite clue. Has she commented on a friend’s ring? Why did she like it? Or why not?
* Does she like diamonds, or does she prefer other gemstones? Has she ever discussed jewelry with friends or family?
* If you’re clueless, don’t worry. It shouldn’t be hard to divert her attention towards a jewelry store when you’re out shopping. Be subtle! Tell her you’re looking for a tie-pin or something, but be sure to stop by the engagement ring counter. Start Noticing Her Hands!
* Think proportional when it comes to choosing the shape of the stone, and the ring’s thickness.
* Bold styles generally suit women with long fingers, while delicate jewelry will be unnoticeable on large hands.
* The wider the band, the shorter the appearance of the finger.
* Oval diamonds will make her fingers look more sleek, but avoid over-doing it.
3. CHOOSING YOUR JEWELER & JEWELRY CERTIFICATION
Regardless of whether you choose a gemstone or a diamond, this is an important step. It will not only ensure you get your money’s worth, but will also help if and when you decide to insure your expensive investment. In the US, the GIA (Gemological Institute of America) or the AGS (American Gem Society) are the most trusted certifiers for diamonds. Various countries have their respective certifiers, so make some enquiries before you purchase that stone. Look for a jeweler you can trust. Generally, a jeweler who has a good reputation in the community and who’s been in business for many years is the one you should approach, especially if you, like most men, are not very familiar with jewelry.
4. The Engagement Ring’s Band
Get It Right! However tempting it is to ignore the band because the vast majority of the cost is for the gemstone or diamond, the way the diamond is set in the band decides the overall appearance of the finished jewelry. Fortunately, this is much easier than picking out the gemstone. The thickness of the band isn’t the only consideration. Her personal taste in metal color, her hand type, her skin color, the size of the stone, all play a part in deciding what the band should look like. Regardless of whether you choose White, Yellow or Rose Gold, 18ct (Carat) Gold is the best choice, followed by 14ct. Despite being significantly more expensive, many still choose Platinum for the ring. Now you need to decide how you want the stone set. Want it to ride low? It won’t be very showy (you’re probably wondering what the point is then), but consider that a diamond that juts out is liable to snag itself on just about anything that brushes it and will also be prone to damage. You’d imagine there’d be an easy answer to the illusive question of choosing an engagement ring design.
There is no scientific or mathematical way to design or choose one. It’s purely a matter of one’s personal preference, hedged by some practical reasoning: – Does it look good? – Is it practical to wear? – Will it withstand normal wear and tear? – Does it hold the all-important gemstone securely? If you want an extremely fine design, then choose Platinum, as it is much stronger and will wear out gold many times over. Also, a 6-claw arrangement will hold the stone more securely than a 4-claw. If her work involves very heavy contact, then you may consider a bezel setting (called a rub-over). It’s safer than a claw setting. You may want to sneak one of her rings to the jeweler, so he can measure it. Otherwise an outline will help. You could impress one of her rings in a bar of soap, or push one down as far as it will go on one of your fingers, then mark the spot. Simpler still would be to trace the ring on paper. If all else fails, try asking her mother or friend to do the deed for you! Which brings us to our final point: Is this ring an investment? Ideally, no. At least, not for the reason you’ve bought it. When you consider the non-monetary investment you’ve made in the ring, you’ll find as a symbol of your love and devotion, it stands unrivaled. As a priceless testament of your love, your woman will be overjoyed, no matter what you choose.
Dichroscope
Dichroscope
by Ritika Changrani
Dichroscope is a tool used to differentiate similar looking gemstones based on the dichroic property of the gemstones.
Some gemstones are singly refractive. They exhibit only one colour to observer. There are also gemstones which exhibit two different colours of light. But most of that is not detected by the human eye since the two colours produced are so close in wavelength that it becomes difficult for the human eye to identify them. The two colours in such gemstones mix up to give a slightly different colour. Such stones are called doubly refractive gemstones. For example, ruby is made up of dark red and light pink colour. But it appears to the viewer as light red.
The property of the gemstone to exhibit two different colours or shades when turned in two different directions under light is called as dichroism. Examples of the gemstones which are Dichroic are sapphire, zircon, tourmaline and topaz.
Dichroscope is a tool used to differentiate similar looking gemstones based on the Dichroic property of the gemstones. Hence it can easily differentiate gemstones like ruby from tourmaline since ruby is Dichroic and tourmaline is pleochroic. Dichroscope also helps to determine Pleochroism and trichorism. Dichroscope helps to determine the optical properties of a gemstone. (image courtesy: www.faceters.com)
Dichroscope is a metal tube which is open on one end and has a lens at the other. It has an optical calcite mounted inside the tube and produces a double image of the square opening. Enough bright light is directed on a gemstone and viewed through the dichroscope. Dichroscope separates the different colours of light into its constituent colours. Light entering the dichroscope is broken into two polarized rays. Two images of different colours indicate that the vibrations are of different wavelengths and at right angles to each other. If dichroism is not detected in the first test, the gemstone has to be turned and output colours must be viewed in other directions too.
Pleochroism can be detected by rotating the instrument at an angle of 90 degrees. If the two colours switch sides on the split image, the gemstone is pleochroic. To determine trichorism, it is necessary to change the orientation of the stone. If one new colour is determined along with one of the colours of previous orientation, the gemstone exhibits trichorism. Trichroic gems show three different colours when viewed in three directions perpendicular to each other. Singly refractive stones produce only one colour on the dichroscope.
How does a Dichroscope work?
Dichroscope works on the principle of plane polarized light. Plane polarized light is the light of a specific wavelength that is separated from ordinary light and travels in a specific direction. Some waves may travel up and down and some side to side. When light traveling in different direction is being separated, it is possible to view the individual colours of specific wavelength.
Types of Dichroscopes
There are two different types of dichroscopes. They are London dichroscope and Calcite dichroscope.
London dichroscope
In a London dichroscope, two pieces of Polaroid orientated at right angles to each other are placed such that the light entering each polarizing filter are at right angles to each other. The two polaroids in a London dichroscope are joined together in same plane. London dichroscopes are much cheaper when compared to the calcite dichroscope but does not give as clear a result as the other. It is difficult to determine gemstones with weak Pleochroism with a London dichroscope.
Calcite Dichroscope
The calcite dichroscope is made up of a calcite crystal. The calcite has a special characteristic called bi-refringent. This property of calcite enables the gemstone to appear doubled when looking through it. The calcite crystal splits the light entering the dichroscope into two rays and thereby helps identify the difference in colours. The two rays form two images at right angles to each other.
Out of the two dichroscopes, the calcite dichroscope is the most commonly used in the gem testing laboratories to test the Dichroic property of the gem stones.
How to use a Dichroscope?
Hold the upper portion of the dichroscope near the eye – may be an inch from your eye. Place the gemstone near the opening. The other end of the dichroscope is hexagonal and hence it is easier to turn the dichroscope while testing. View the gemstone through the gem view opening. Slowly rotate the dichroscope to complete one full rotation and observe the colour difference of the two small squares which appear inside the dichroscope while you rotate. If you observe two colours while you rotate, the gemstone is dichroic. If three colours are observed, the stone is trichroic. Repeat the observation to confirm the number of colours observed. Observe the strength of the colours as it helps determine the type of gemstone. Always make sure that sufficient bright light is focused on the gemstone while you observe the colours using dichroscope. Never use fluorescent light since it can give a false result.
Advantages
- Dichroscope helps determine the pleochroic property of the gemstone which helps to separate different types of gemstones.
- It also helps to determine whether the gemstone exhibits weak Pleochroism or strong Pleochroism.
- Dichroscope also helps identify some gemstones.
- It also helps to study the optical properties of the gemstone
Polariscope
Polariscope
by Ritika Changrani
Polariscope is an instrument used in gemmology which helps to find if the gemstone is single refractive or double refractive and also allows determining the various crystal axis of the stone.
A Polariscope is used to determine whether the gemstone is natural or synthetic. This is one of the most commonly used instruments by the gemmologists. The use of plane polarized light allows us to see the actual path the beams are taking through the stone.
A polariscope is made of two Polaroid plates that rotate, a power switch, a stone holder and a bottom light source. Two polarized filters or plates are made of polarizing plastic sheets, one is on the top of the instrument, known as analyzer and the other is on the bottom of the instrument, known as polarizer. Polarizer and analyzer have their own vibrational planes. When the vibrational plane of polarizer and the vibrational direction of the analyzer are at right angles to each other, the field between them appears dark. This position is known as crossed position and it is in this position that the gemstones are tested to see if they are isotropic, anisotropic, anomalously double refractive and anisotropic aggregate. The polariscope can be used to determine the optical character as well as the optical sign of the gemstone.
Polariscope can also be used to determine the strains in diamond. It helps in separating natural gemstones from synthetic ones and also helps to distinguish solid inclusions from negative inclusions. Polariscope can also be used for recognizing polysynthetic twinning.
How to use a Polariscope?
- The polariscope is adjusted for cross position by setting the vibrational plane of polarizer and the vibrational direction of analyzer at right angles to each other.
- Turn on the light source and place the gemstone on the rotating platform above the polarizer. The gemstone is rotated in a vertical axis.
- Observe the gemstone through the analyzer and note down the observations
- Based on the observations the nature of the gemstone can be determined as follows.
- If the stone remains dark throughout the 360 degree rotation, the stone is said to be isotropic or singly refractive.
- If the stone darkens evenly at every 90 degree interval, the stone is said to be doubly refractive or anisotropic.
- If the stone appears light throughout the rotation, it is said to be microcrystalline or crypto crystalline aggregate.
- If the stone shows anomalous double refraction, the stone is singly refractive. Anomalous double refraction may be confusing at times. Hence when there is a suspicion that about anomalous double refraction, it is recommended to orientate the stone in the position where it appears lightest. Then turn the analyzer to 90 degree. If the stone appears lighter than before it is said to exhibit anomalous double refraction and hence is singly refractive. If the stone appears the same, it is doubly refractive.
How does a Polariscope work?
Polariscope works on the principle of plane polarized light. Single refractive gemstones do not break the plane polarized light into various colours. There is only one beam of light coming out. Examples of singly refractive gemstones include diamonds. Double refractive gemstones break the plane polarized light into two paths. One is the ordinary beam and the other is the extraordinary beam. Based on analyzing the transmitted light, the nature of gemstone can be identified. Some of the doubly refractive gemstones are quartz, tourmaline, ruby, zircon, peridot, sapphire and rulite.
Both the filters i.e. polarizer and the analyzer are turned to the dark position. When plane polarized light is passed through the gemstone, the singly refractive stone remains dark since it does not change the path of light. Hence it remains dark when observed in all positions. But in case of double refractive gemstone, when plane polarized light is passed through it, the stone changes the path of the light and hence the direction of the light wave changes. This produces light that is no more polarized. The change in direction of light makes the stone change from light to dark as it is rotated between the Polaroid plates.
Since the polariscope works through plane polarized light, it can be used to test transparent as well as translucent gemstones, but cannot be used to test opaque materials. Once the stone is found to be doubly refractive, a conoscope can help to determine the optic interference figure. Optic interference figure helps to locate the various directions in which the light is traveling through the stone. This information in turn helps to identify the type of gemstone. The different shadow patterns observed through the polariscope helps to determine the crystal structure and diagnostic patterns of the gemstone.
Types of Polariscope
There are two types of polariscope i.e. plane polariscope and circular polariscope. Circular polariscope work on circular polarized light unlike plane polariscope which works on plane polarized light. In a circular polariscope, two quarter wave plates are added to plane polariscope. One quarter wave plate is placed between the polarizer and the gemstone to be tested and the second quarter wave plate is placed between the analyzer and the gemstone. The quarter wave plates produce circularly polarized light. The advantage of using circular polariscope is that it helps distinguish isochromatics and isoclinics. But plane polariscope are more extensively used for testing gemstones.
ENGAGEMENT RING BUYING GUIDE BY PRASAD
by S Prasad
Platinum, known for its durability is a popular choice for rings. Finally, the selection of the ring style is just as important. You could either select a simple ring with a single stone (which is called a solitaire), or a ring with side stones or Baguettes, which will add to the total price of the ring and is more personalized.
Summary:
A special occasion always warrants a special gift. And for an occasion like an engagement, the ring is the gift which highlights the ceremony. When buying an engagement ring, the first decision to make would be the ring size. It is important to note that the ring band (or the part of the ring which surrounds the finger) should fit comfortably and well. The engagement ring itself comes in two parts: the setting (which holds the stone) and the band. The setting is almost always made out of platinum (even on a gold ring) because of the metal’s strength and durability.
A selection can be made whether the stone is gripped by 4 or 6 prongs. A setting with 4 prongs will show more of the stone, but a setting with 6 prongs is more secure. But, whether you would want prongs or any other setting which does not use prongs, for example, a setting which would use a channel to hold the stone, is a matter of personal preference. The band itself can be made out of different materials, most common to note would be gold. The gold used in manufacturing rings is usually alloyed with Nickel, Copper or Zinc to add strength to the band, as pure gold is known to bend easily.
A 24-carat band is known to be of pure gold, where as an 18-carat band will usually be about 68% gold. However, if you would want a silver band that rarely tarnishes, platinum is the metal of choice for the band. But, platinum is much more rare than gold and costs more. Platinum, known for its durability is a popular choice for rings. Finally, the selection of the ring style is just as important. You could either select a simple ring with a single stone (which is called a solitaire), or a ring with side stones or Baguettes, which will add to the total price of the ring and is more personalized. 2. How to choose gemstone. A gemstone is a mineral rock or petrified material that when cut and polished, can be used as either a collectible or in Jewelry. It is usually the organic or hard gemstones like diamonds and rubies which are used in Jewelry. There are four basic gemstones which are considered as cardinal and these are Diamonds, Rubies, Sapphires and Emeralds; and these are classified as precious stones. Others, which are semi-precious, range from Agate to Zircon, which are mostly manufactured to imitate precious stones.
The most common semi-precious gemstones are Opal, Cubic Zirconia (which is a synthetic diamond substitute), Amethyst, Jade, Quartz, Topaz and Lapis Lazuli. When selecting a gemstone, some important factors to consider would be: a) The artificial materials used in the gem: Some artificial materials used include High-Lead glass, and synthetic materials like cubic zirconia, corundum, and moissanite. These are used to strengthen the material. b) The organic materials used: these can range from Amber, Bone, Coral, Pearl to Jet (Lignite). c) The cut of the stone: Some stones, most commonly diamonds, are cut into different geometrical shapes to reflect their dimensions. Most common cuts are Round, Radiant, Pear, Oval and Marquise. The cut defines the shape of the stone and determines the brilliance it reflects. It is the above factors which also determine the price of the gemstone in addition to the setting that the gemstone would be in, the carat weight and the color.
Refractometer
Refractometer
by Ritika Changrani
A Refractometer is a gemmological tool used to find the ability of gemstone to bend or refract light. This measure is the refractive index of a gemstone.
A Refractometer can be used to measure the refractive index of both singly refractive (isotropic) and doubly refractive (anisotropic) gems. The refractive index helps to determine the composition and physical properties of gemstone. With the help of refractive index, it is easy to identify the type of gemstone. Also, it is possible to estimate the amount of impurity present in the gemstone by comparing the measured refractive index with the standard value of the natural gemstone. With the help of Refractometer, birefringence and optic sign of the gem can also be determined.
How does a Refractometer work?
Refractometer works on the principle of Total Internal Reflection i.e. when light travels from denser material or the material with higher refractive index to rarer material or the material with lower refractive index, the light reflects into the denser material or refracts into the rarer material depending on the angle of incidence of the light traveling. (image courtesy: www.diamondtech.com).
Refractometer is made of a metal case, polarizing filter on the top, glass hemicylinder and viewing lens at the bottom. Natural or white light is passed through the back of the unit. The light travels through the glass hemi cylinder and then to the gemstone which is placed on the glass hemicylinder using a special refractive index liquid, which seals the gemstone to the hemicylinder thereby removing the air in between them. This is done to maintain the same speed of light in both the glass hemicylinder as well as stone so that the refracted rays obtained are accurate. The light is then refracted and sent to the viewing lens through the glass hemicylinder. Through the viewing lens one can see the refracted rays of light. The bending or slowing of light caused by the gemstone appears as the light and dark area combined by thin green line. The green line thus obtained is the refractive index of the gemstone.
A Refractometer is designed such that the incident and exiting rays reach the boundary of hemicylinder at 90 degree. No refraction occurs when the light ray is at 90 degrees to the boundary. Therefore no refracted rays are visible and hence appear as dark areas on the scale. The reflected rays of light appear as the light areas on the scale of the Refractometer. The light and the dark boundary on the scale is the representation of critical angle.
How to use a Refractometer?
- Apply a small amount of refractive index liquid on the metal base near the hemicylinder. Slowly place the gemstone on the refractive index liquid. Then slide the stone to the centre of the hemicylinder. Take care that you don’t apply pressure on the stone as it may damage the hemicylinder. The liquid builds optical contact between the stone and the hemicylinder.
- Close the lid of the Refractometer to avoid external light.
- Place the light source at the back of the Refractometer. Adjust the beam until you see bright light when you observe through the viewing lens.
- Position your eye such that you can see the whole scale through the viewing lens without moving your eye. This is to avoid the parallax error in the reading.
- Move your head up and down until you can see the clear separation of light and dark areas. Note down the reading on the scale where the thin greenish line appears.
- Unscrew the polarizing filter and place it on the viewing lens.
- Take down the reading. Rotate the polarizing filter to 90 degree and note the readings.
- Polarizing filter helps to determine if the stone is singly refractive or doubly refractive. If the stone is singly refractive, only one shadow edge is seen. Note down the readings rotating the stone 135 degrees.
- If the stone is doubly refractive, shadow edges move between two values on the scale. Note down the two values, i.e. the upper and the lower value. Take down four sets of reading by rotating the stone to 45 degrees.
- If one of the reading i.e. either upper reading or the lower reading remains same, the stone is said to be uni-axial. If both the readings change after rotating the stone, the stone is said to be bi-axial.
- The refractive index is the difference between the largest higher reading and the smallest lower reading.
- f the difference is positive, the optic sign of the stone is positive; else the optic sign of the stone is negative.
Tips to Remember while using a Refractometer
- Store the equipment in a dry place to protect the device from moisture which can affect the accuracy of the equipment.
- While you move the gem stone on the glass hemicylinder, take care to move the stone slowly so that no scratch is caused on the hemicylinder. A minute scratch causes can damage it and turns costly to be repaired.
- The refractive index liquid has to be stored and sealed. Avoid its contact with hands or eyes.
- Make sure to use the tiniest drop of refractive index liquid since the liquid itself has its own refractive index and causes total internal reflection between hemicylinder and the liquid. This will in turn affect the accuracy of the reading.
- The contact liquid should be selected with proper care since it sets the limit to the stones tested. The stones with greater refractive index than the contact liquid cannot be tested and hence give negative reading.
- Make sure there is adequate amount of light. White light can be used while testing, but monochromatic yellow light is widely used. White light can give good results for single refractive stones, but for doubly refractive gems sodium light source is the best option. White light, when used with doubly refractive gemstones causes overlap of the refraction readings thereby getting wrong results. Also, the use of sodium light source clearly differentiates the boundary between dark and light areas and hence helps take the readings easily.
ENGAGING INFO FOR THE MAN-TO-BE-ENGAGED
by Sunaina Joseph
The element of surprise is one that you must never compromise on. So don’t make the mistake of asking your partner what she wants, no matter how unsure you are. The average time taken to pick a ring is between one and two months.
Summary:
The Ring. The Circle. The symbol of unity, perfection and eternity. Like the Sun and the full Moon. It has no beginning and no end. Ever wondered where the tradition of the ring started from? I’ve heard many stories and this is the one that is probably the closest to the truth. It is said that thousands of years ago, the caveman used a woven cord of rushes, grass, reeds and leather to tie the hands and feet of his potential mate so that she could not escape. After a while, he tied it only around her hands. Finally, when he was certain that she would stay with him, he would tie the cord only around her finger. Now, we do it like our forefathers, and their forefathers, hence carrying on thousands of years of tradition. The only difference is that we have a little more trouble choosing our rushes and reeds.
I have a few tips for those on the brink of asking the ‘big question’, but before we get down to the facts and figures, lets make one thing absolutely clear- This ring is bought only once in your entire lifetime, so it must be as unique as the woman you have chosen.
BASICS BEFORE FACTS
The element of surprise is one that you must never compromise on. So don’t make the mistake of asking your partner what she wants, no matter how unsure you are. The average time taken to pick a ring is between one and two months. Don’t rush it. It never turns out right if u do. Conventionally, the two-month salary is the yardstick, but in the end it is entirely up to you. Keep in mind that you will end up spending a little more than you originally intended. The Classic Engagement Ring is made up of three parts- The Band, the Stone and the Setting. If you make a decision on the type of metal you want, you are definitely onto a good start.
THE BAND
‘The true measure of value is rarity’. Platinum is rare, it is eternal and it should be at the top of your list (if it is within your budget). Any design that you see in a store can be duplicated in platinum. The hallmark of the ring will reveal the metal that makes up the ring. Indications of platinum are: Platinum, Plat, Pt, Pt950, 950Pt, 950Plat, Plat950, 900Pt, Pt900 and 900Plat. Yellow gold is the next best option. It has been popular in jewelry-making since the beginning of time as it bends easily. White gold is not a very good choice as it turns yellow after a while, and has to be replated. Tip: Observe the kind of metal your partner usually wears. Stick to what you think she is most comfortable with.
THE STONE
The stone will account for the major cost of the ring (approximately 75-90%) Here again, beauty, rarity and value are the criteria, hence the diamond has become the choice of the masses over the years. When choosing your diamond, keep in mind the four C’s- Color, Clarity, Cut, and Carat weight. The Solitaire (single diamond) of 1.0 carat is most widely favored among the women, but there is a wide variety of styles that makes the ring more individualized.
You may choose pear shaped or oval stones (though round diamonds are usually preferred by the bride-to-be) For a more decorated ring, side stones and baguettes can be added. This will add to the overall appeal and cost of the ring. The in-thing is diamond laser inscription. You can inscribe a romantic message, poem, symbol or just anything to personalize the diamond. If this is not what you are looking for, remember that diamonds are not your only choice. If you have a tight budget, or your partner is not a fan of diamonds, there are other options. Queen Elizabeth and Princess Diana received sapphire engagement rings. So follow your heart, and some of my advice.
A Ruby, Red Garnet and Red Tourmaline are symbols of the heart. Red is a sign of passion and zest for life. Green symbolizes faithfulness, loyalty and continuity. Hence the Emerald, the Green Tourmaline and the Green Garnet are favored stones. Similarly, the Sapphire, Spinel, Iolite, and Blue Tourmaline are symbols of spirituality and purity. The gem that has been associated with love and marriage the longest is the natural Pearl, which is a great choice if the style of the ring is antique.
THE SETTING
This is what holds the stone in the band, and it is important that you choose the appropriate setting (for aesthetics and practicality)).The most commonly used settings that hold the stone securely are the 4 or 6 prongs(6 prongs are recommended for the security of the stone) and the channel setting . Some stones are held in place with pressure. Style is the next issue to tackle. There are various styles such as contemporary, retro, antique reproductions and classics, to name a few. This, too, can be chosen in accordance with the style of your partner. Find something that will complement the kind of clothes she wears, or take a look at her home dicor. Is it minimalist and sleek? Then go with something simple, yet modern. If she has funky, chic furnishing (the flea market look), then you should opt for something more Art Dicor. If her house is draped with sheer fabrics, dripping with rose petals and smelling of scented candles, then Art Nouveau is the ideal choice. BONUS TIPS Tip1: There are different finger types, and the ring must be chosen to suit the hand of your partner. Think proportional! Do not choose wide bands for short fingers, as they make fingers appear shorter than they are.
Women with long fingers can carry off even a bold style, whereas an extremely delicate ring can be lost on large hands. Tip2: Her lifestyle can determine the kind of jewelry she wears. If her workplace can’t handle fussy jewelry, then make sure you choose something subtle. Tip3: If you can’t get a hold of her ring size, don’t panic. Jewelers can easily resize the ring later. …….. And after all this, if you still cant figure out the ideal combination of metal and stone…. and whatever you do, the stone seems too big or too small for the band… and the band ends up being the wrong color and the wrong size. If you are still as lost as when you started your quest, and are at your wits end, buy a loose stone, ask her the big question, and the both of you can shop together for the perfect ring!
Spectroscope
Spectroscope
by Ritika Changrani
A Spectroscope helps to identify cut stones, rough stones, mounted stones and unmounted stones to see whether they are real or fakes.
A Spectroscope is a gemological device used to test if the gemstone is natural or synthetic. Spectroscope helps to determine what parts of white light are being absorbed by the gemstone.
White light is made up of seven different colours namely violet, indigo, blue, green, yellow, orange and red, which have different wavelengths and travel with different speed. When white light is passed through a gemstone, a part of it, based on the energy level is absorbed by the gemstone and the remaining colours combine to give a different colour to the stone. When observed through the spectroscope, one can see bands or colours missing. The missing bands are the colours absorbed by the gemstone. The colours absorbed let us know the elements present and the chemical composition in the gemstone which thereby helps in gemstone identification.
Types of Spectroscope
There are two types of spectroscope, diffraction grating spectroscope and prism spectroscope.
Diffraction Grating Spectroscope
Diffraction grating spectroscope implies the principle of diffraction. Diffraction refers to the bending of light waves around a sharp edge or an obstacle by transmission or by reflection. This type of spectroscope is made up of high-dispersion diffraction grating film, movable slits and a photo detector which is used to measure the properties of light within the specified portion of the spectrum. Here light is made to enter a narrow slit. The light is then diffracted by thin high-dispersion diffraction grating film. This causes uniform spectrum image and disperses light into large visible spectrum. The advantage of diffraction grating spectroscope over the prism spectroscopes is that the spectrum is evenly distributed and hence is easier to read. But the spectrum thus produced is not as bright as that produced by prism spectroscope. Diffraction grating spectroscopes do not have an inbuilt calibration scale.
Prism Spectroscope
Prism spectroscope works on the principle of dispersion. Dispersion is defined as the splitting of white light into its constituent colours. Prism spectroscope is made of three optical grade glass prisms placed in optical contact with each other. Most of the prism spectroscopes come with calibration scale. But experienced people make observations without the scale.
In a prism spectroscope, light is made to enter through a narrow slit which is dispersed by passing through a series of prisms. In prism spectroscopes, the spectrum obtained is brighter and faint lines are clearly visible. But the disadvantage with prism spectroscope is that the spectrum is not evenly distributed. Blue parts are more spread and red parts are more condensed. It is difficult to distinguish lines in red part since they are very close to each other. Prism spectroscopes come with focus slide control and light slit control which allows adjusting for the amount of light entering the unit.
How to use a Spectroscope?
- First of all, before testing for the absorption spectra of the gemstones, hold the spectroscope against some different sources of illumination. Holding it against either a fluorescent light bulb or a computer monitor shows clear absorption bands.
- Place the gemstone on a black non-reflective surface may be a piece of black velvety cloth. If the surface is non-reflective, the observations may not be accurate and hence give false readings.
- Place the source of white light such that light enters the pavilion of gemstone at an angle of 45 degrees.
- Place the spectroscope on the other side at the same angle. The angle of 45 degree is chosen since this is the path in which light travels in the longest path picking up most colours.
- The other way of positioning can be by placing the light source and the gemstone in one line such that the light illuminates the gemstone from the back. This helps to view the gemstone in transmitted light.
- Note the observations through the spectroscope. Note down the spectrum seen with red end of the spectrum on the left and violet end of the spectrum to the right. The colours which are absorbed by the gemstone appear as missing bands. The colours absorbed mix up to give the gemstone a different colour.
- Based on the spectrum obtained, you can analyze the composition of the gemstone and hence determine the type of gemstone.
- The spectrum can also be compared with that of a known gemstone to identify if the gemstone is a natural or a synthetic one.
Though spectroscope is one of the important tools in gemology, it should be purchased only when it is extremely necessary. The cost of spectroscope is quite high. Furthermore, only experienced gemmologists can make use of the spectroscope more efficiently. It is difficult for an inexperienced person to study the nature of gemstones using a spectroscope.
ENGAGEMENT RING BUYING GUIDE BY NALINI
by Nalini Naik
First and foremost you will have to ascertain her taste where jewelry is concerned. Find out whether she likes settings that are simple and sophisticated, or styles that are bold and colorful. Is she partial to any particular gemstone? Then there is yellow gold or white gold for the band to choose from, or even platinum.
Summary:
An engagement ring is a very important piece of jewelry because, it is a symbol of a commitment to care, to love, and to cherish. It is a promise of togetherness for a lifetime. So, the utmost care has to be taken when choosing the ring or this very important occasion. Buying an engagement ring is not one of the easiest of tasks. But, with a little help and guidance, you will be able to acquire a beautiful ring which will bring a sparkle to her eyes. So here are a few guidelines to help you select the ideal engagement ring:
Her choice
First and foremost you will have to ascertain her taste where jewelry is concerned. Find out whether she likes settings that are simple and sophisticated, or styles that are bold and colorful. Is she partial to any particular gemstone? Then there is yellow gold or white gold for the band to choose from, or even platinum. One way of determining this is by the kind of jewelry she already possesses and wears. You can also enroll the assistance of a close friend or close relative. Once you are fairly sure of her choice in engagements rings, the next step is to decide your budget.
Your budget
How much are you willing to spend or better still how much can you afford? With a wide array of diamonds and other gemstones and other gemstones to choose from, the sky is the limit. But if your budget is limited, do not worry. One can acquire beautiful rings made of diamonds, rubies, emeralds and sapphires or even semiprecious stones at a most affordable price. So, you don’t need to set your targets too high. With good taste and a little creativity you can buy a ring which is impeccably stylish and sophisticated. Remember, great style does not always comes at a great price. Once your budget has been decided, your next step would be to make sure you get value for your money. In order to do this a fair knowledge of diamonds and other stones will go a long way in helping you make the correct choice. You will have to know the variety that is available and how to determine their quality. Armed with this knowledge you will be able to get the very best they have to offer, and within your budget.
So let’s begin by making a study of diamonds and their characteristics. Diamonds; they say diamonds are forever. How true! This gem which is called a girls best friend, is known for its durability and beauty. But, all diamonds are not the same. They not only vary in size, but also in their quality. This is what determines their price too. For example solitaires of one carat and more are the most expensive. And as for their quality, this is determined by their cut, clarity, color and carat. To know a little more about the four ‘Cs’ as they are called, lets go into them one by one.
Cut: This important aspect is what gives the diamond its brilliance and fire and sets it apart from the other gems. The light reflecting off a beautifully cut diamond is what adds to it’s sparkle and luster. A diamond that is not so well cut looks dull and lifeless. In fact before you make a final choice make sure the diamond sparkles beautifully in natural and artificial light. Remember, an ideally cut diamond has perfect proportions,
Clarity: The best diamond is the one without any spots and discoloration. It should be absolutely colorless and clear. In fact the value of the diamond is also determined by it’s clarity. The more spotless and clear the diamond is, the more value it will have. Sometimes the spots and discolorations are very visible to the naked eye, but most times they are not. This is why most of the reputed jewelry outlets offer magnifying glasses to their customers. When viewed through a magnifying glass, any spot or discoloration is visible immediately. So take a good look before you make a final choice.
Color: The white diamond devoid of any color or spots is rare and most valuable. These are most favored. Of course there are colored variations available too. But these are not very expensive or popular because of the many impurities present in them.
Carat: The carat or the measure of the size is what makes it more or less valuable. The bigger the diamond the more expensive it is. A solitaire weighing a cart or more is definitely more expensive than cluster of small diamonds adding up to the same carat weight.
Thus, keeping all the above mentioned factors in mind one can make a fairly good choice. But before making a final decision lets learn a little more about the gems. Gemstones like rubies, emeralds and sapphires are quite valuable, though not as much as diamonds. These three varieties are popularly used in celebration rings. These may be used on their own or mixed with other gems and diamonds. The dark green of the emerald, the deep red of the ruby and the mystic blue of the sapphire, all complement each other as well as the diamond, when used along with them. The vibrant colors of these gems has to be seen to be believed.
Rings crafted intricately with these precious stones never go out of fashion. Keep in mind some important points when choosing these gems- the gems should not be chipped or cracked. The color should be even as far as possible. Like diamonds, the cut and clarity is important and their prices vary with their size. All these gems come in various shapes too. The band and ring setting has to be decided on next- the band could be 14k or 18kgold. The gold could be yellow or white, These bands studded wit diamonds and precious stones could take your breadth away. Then there is platinum. Bands made of platinum are best suited for solitaires because they hold the stone much better. Of course, platinum looks god with small diamonds too. As for the setting, a cluster of small diamonds, set in different patterns, can look impeccably stylish. And when mixed with other gems, like emeralds, rubies and sapphires, they look stunning .
All in all, you can get settings from the classic to the contemporary styles. So the choice is very wide indeed. When choosing a pattern, follow your instinct, and you cannot go wrong. But all said and done, if your budget permits, I would recommend a solitaire. It is a once in a lifetime buy, and no woman young or old can resist the allure, the mystic and charm of a solitaire. One last piece of advice. Always buy gems from reputed jewelry outlets. These give you a buy back guarantee as well. Make sure the gems, especially diamonds are certified. Check out with different jewelers before making the final choice. This way, you’ll get the best your money can buy And last but not the least, do not forget to create the perfect ambience and mood , when presenting the ring. Good Luck.