Agate Facts and Buying Guide
by Sheweta Dhanuka
The variety of colours found is immense yet some common colours are green, yellow, purple, black, orange, brown, red, reddish-brown, white and bluish-white etc. Colour change takes place due to change in the impurities and its content in the chemical composition such as red occurs due to presence of either one of the mineral viz. iron, chromium, cobalt or cooper.
Agate is an innovatively created gemstone by the nature. It belongs to the chalcedony quartz family. It was found thousands of years ago in Achates River in southwestern Sicily that is now know as Dirillo River. The name Agate is derived from the initial name of the river-achates. It is the birthstone for the month of May and anniversary stone for 12th year of marriage.
This is an attractive semi precious gemstone with huge diversity in it. Easy availability, moderate price, good looks etc are few features that make it well liked in the circle of gemstone lovers. It is a simple stone without much specification hitherto general awareness about it is essential while making the purchase. This article provides the all-purpose information that could also be used as buying guide. Agate occurs in many different forms but here only few imperative varieties are mentioned. The characteristics discussed are about Agate as a whole not specific to any one single variety.
Varieties – It is procured in varied forms. To know this gemstone well, one has to be aware of its varieties too. All forms are used as gemstone and ornamental stone. These differ from one another due to the change in impurities in the composition. The varieties are differentiated on the basis of colour of the bands.
Moss Agate: It is a clear stone, green in colour and contains visible impurities. It is also known as Mocha stone. This is the most-sought-after variety. It is considered close to nature and said best suited for those related with agriculture industry. Helps in creating the balance within the sides of brain.
Dendritic Agate: It is black or white in colour. The structure of this form of Agate is that of tree with trunk having big and small branches. It contains manganese oxide impurities that form the fabrications and so on.
Riband Agate : In this gemstone, the bands are broad and appear as straight lines across the gemstone. It is also known as ribbon agate.
Ring Agate : As the name suggests, it comprises of bands in form of concentric circles in varied colours. It is also called as eye agate.
Plume Agate: It is named after its plume like shape. Colour varies from shades of blue, white, yellow and red. United States of America is the primary source for this variety.
Fire Agate: The formation process of this variety is quite distinctive. Like all it is also produced during the volcanic eruption or in basalt. It is layered in one micro-thin layer in vugs from hydrothermal solution at a time. Similarly few more layers are formed then among these layers some reflect light back in the pattern of rainbow giving rise to bubbles and sheets of different colours viz. brilliant blue, red, yellow and green.
Colour – This fascinating gem is available in varied colours. The variety of colours found is immense yet some common colours are green, yellow, purple, black, orange, brown, red, reddish-brown, white and bluish-white etc. Colour change takes place due to change in the impurities and its content in the chemical composition such as red occurs due to presence of either one of the mineral viz. iron, chromium, cobalt or cooper. Black owes its colour to iron and manganese. Green is due to iron, chromium, nickel and copper while blue is because of iron, titanium and cooper. Iron oxide leads to brown, chromium to yellow and manganese to pink and violet as well. Apart from the impurities, colour is also affected by change in temperature, radiation, pressure and weather.
Bands are the distinctive feature of this colourful gemstone. Each and every stone possess concentric bands in different colours and textures. These bands are formed when impurities reacts with the solidifying gel in the volcanic lava at the time of crystallization. Difference in bands occurs because of the variations in the impurities and its content in the composition of the stone. This process is entirely natural therefore no two stones would have similar bands. Furthermore the pattern of bands is irregular. It could be circular, patches or haphazard lines etc.
Clarity – It is vitreous to glassy in luster. Being, translucent or opaque in nature the presence of flaws or inclusions is not of much significance. Moreover, while processing the rough into a gemstone, through cutting and polishing the presence of flaws further becomes unnoticed. In this stone clarity is not much helpful while making the purchase of a genuine stone.
Cut – This trait is very crucial. The end look of the stone is reliant on the cut it is given. The natural bands of stone are enhanced if given the appropriate cut therefore; cutters have to concentrate on the bands while cutting. It is a hard stone thus, it can be given any shape like round, pear, square, emerald and so on.
Carat Weight – In natural state this marvelous gem is found in large and massive form. At the time of preliminary gemstone processing, the rough is cut and polished to create medium and smaller stones of different carat weight. As per one’s pocket one can select the suitable stone of any carat. Gems between 2-4 ctw are apposite for the jewelry items and gives splendid look as well. This weight is neither less nor more and is affordable too. The stones used for creating the ornamental pieces has to be between 4-9 carat or even more.
Price – This awesome gemstone could be acquired easily as it is available at reasonable price. Only few stones with extraordinary bands or scenes are priced more yet affordable. The price is ascertained on the basis of carat weight, cut and bands structure. Price increases with the increase in carat weight. A good cut that highlights the bands enhance the beauty of the gem hence is worth more. Bright stones consisting of unusual and exclusive bands are valued more in terms of money. The sculptures and carved pieces made of one single solid piece are priced higher than those items where more than one stone is used.
Occurrence – It generally occurs as rounded nodules or veins. It comes into existence during the volcanic eruption in the cavities of eruptive rocks or the volcanic lava. After the volcanic eruption, flowing lava starts solidifying then few gas bubbles are trapped in it. These bubbles later are filled with alkali and silica-bearing waters, which set as gel. Then alkali and iron present in the surrounding lava reacts resulting iron hydroxide forming the bands within the gel. Finally, gel looses water and crystallization occurs leaving the bands in one piece. It forms in shallow depth and low temperature.
Source – This colourful gemstone was first mined at Nahe River valley in Germany. Nahe deposits are now said to be exhausted. Today, it is found across the globe. The next larger producers are Brazil and Uruguay. Some other countries proffering agate are Mexico, Egypt, Congo, Italy, India and Nepal. It is generated in immensity at Oregon, Washington, Idaho and Montana states of USA.
Enhancements – It is porous in nature thus, often artificially stained or dyed to enhance the appearance. Enhancement helps in increasing the net value of the gemstone. The skilled people perform all the treatments and the retention of the changed appearance of the stone lasts for many years.
Imitations – This gemstone comes in many different colours. It is procured quite easily. It is priced moderately still many jewelers sell poor quality stone as agate. Glass agate and Iceland agate are basically poor quality of obsidian that are treated and later sold as agate. Similarly, glass opal stimulant is named as Lake Superior fire agate or Mexican agate and sold at the price of pure agate.
Use – It has jewelry, ornamental and industrial use. Treasured a lot by the lapidaries. Carvings, cameos, intaglios and beads made up of this gemstone cherished by many people. As ornamental use, splendid figures and sculptors are created from large stones. Agate bowls, letter openers, crockery handles, paperweights, bookends and guitar picks are also fairly popular. These are ideal for decorating the house, office and guesthouse etc. Beads are created in striking cabochon shape are used for making exquisite flat or rounded ornaments. Apart from cabochon, other possible shapes are oval, round, baroque and square. The size varies between 1mm to 9mm. Bracelets and necklaces of beads are pretty in demand among the females in almost every corner of the world for casual and professional attire.
Handcrafted jewelry items are made from the well-created stones of different carat weight. Earrings, pendants, broaches and rings made from this gemstone are likes by females in every corner of the globe. It is idyllic for jewelry worn for daily basis. Sterling silver, 18K yellow gold, 18K white gold and platinum are used for making these ornaments. However, silver is used maximum amongst all the accessible metals. The reason being, silver enhances the beauty of the gem more than yellow gold. White gold and platinum are used less because two of these metals are not suitable in the economic terms. For industrial purpose, it is used in the manufacture of grinding equipment.
Precautions – It is rated between 6.5-7 Mohs on the hardness scale. Its hardness rate specifies it as sturdy and long-lasting stone. Therefore, any specific care is not required yet general gemstone precautions are essential for the lifetime retention of the stone. Although the gem is hard and do not requires much care but by taking the precautions the gem and its jewelry would always look as up-to-the-minute.
Beliefs – In ancient times it was used as powerful amulet or talisman to protect the wearer from all dangers and provide necessary strength. European royal families had passion for collecting bowl made up of Agate that can be seen even today in European museums. In past people used to wear it in order to attain the power to overcome the enemies and acquire wealth. Greeks used it for protecting themselves from hazards of sea.
Today astrologers suggest this stone for curing all sleep allied problems like nightmares, bad dreams etc. It is also helps in remedy of insomnia and pancreas turmoil. Blood circulation smoothens by wearing this colour versatile gemstone. Apart from the medical treatments, it creates the balance between the physical, emotional and spiritual state of the wearer. Enhances the analytical ability and improves perceptiveness. It eliminates and cleanses the negative energies from the body.
This multi-faceted gemstone is plain and elegant. It can be worn on different occasions. Try wearing this marvelous gemstone and experience the feeling of eternal joy and happiness. Worth trying !!
Agate Facts
| Chemical Composition | It is silicon dioxide and the chemical formula is SiO2. |
| Colours | Green, yellow, purple, black, orange, brown, red, reddish-brown, white and bluish-white. |
| Streak | White. |
| Refractive Index | 1.545 – 1.554 |
| Specific Gravity | 2.57-2.64 |
| Luster | Vitreous to greasy. |
| Solid State | Translucent. |
| Crystal System | Trigonal. |
| Hardness | 6.5-7 Mohs |
| Cleavage | None. |
| Fractures | Conchoidal. |
| Luminescence | None |
| Birefringence | Weak, between 0.005-0.009 |
| Enhancement | Regularly dyed or stained to improve the colour. |
| Source | Germany, USA, Brazil, Uruguay, Mexico, Egypt, Congo, Italy, India and Nepal |
| Precautions | General gemstone precautions to be taken. |
Nature has given the Agate gemstone the most creative of stripes and colors. It is the chalcedony quartz in concentric layers that give it its variety and a range of colors.
In Mexico, agates are found primarily in the states of San Luis Potosi and Aguascalientes. They are known for their fire agate and the multicolored fire agates are found in Calville in Aguascalientes. Another very beautiful agate is called the Apache Agate which is characterized by its floating red colors that can be seen in the clear agate. Southeast of the area of Apache agate are the cousins called the Laguna and Coyamito are part of the banded agate groups but the Apache Agate still stands apart from them. Here the bands are not as sharp as other agates found in Mexico.