Spinel Facts and Buying Guide

by Sheweta Dhanuka

Many crown jewels of royal families had Spinel instead of precious gemstone Ruby. One such example is Black Prince’s Ruby set in the British Imperial State Crown has less valuable Spinels in place of expensive Rubies. This was a mistake or a well-planned attempt of the jeweler, is still a big enigma. At the first glance, it is almost impossible to distinguish between the two.

Spinel is one of the most beautiful and rare gemstone in the treasure of Mother Nature. Its name is derived from the Latin word ‘spina’ that means ‘thorn’ in reference to the pointed shape of the stone. It was found thousands of years ago. Since then it is an important part of jewelry.

This beauty possesses a secret history. Many crown jewels of royal families had Spinel instead of precious gemstone Ruby. One such example is Black Prince’s Ruby set in the British Imperial State Crown has less valuable Spinels in place of expensive Rubies. This was a mistake or a well-planned attempt of the jeweler, is still a big enigma. At the first glance, it is almost impossible to distinguish between the two. Both these gemstones are very much similar to one another chemically and also in the physical properties. Thus, Spinel is considered as poor man’s ruby. Here we discuss about this gemstone in detail.

Colour – It occurs in many colours but it is generally identified with bright red colour as that of ruby. Red colour appears due to the presence of chromium in its chemical composition. Blue is one more colour that is treasured most like bright red. Other colours are green, orange, mauve, violet, yellow, purple, brown and black. These colours are the result of different impurities of elements in the composition.

In the gemstone market, different colours are designated specific names. Orange coloured gemstones are known as Flame Spinels. These are bright orange without too many blackish overtones. Cobalt Spinels/Blue Spinel is the name for intense blue colour. These are highly sought after by gemstone collectors. The name Ruby Spinel is for bright red colour while Rubicelle for yellow to orange colour. Pink to pale red colour is called as Balas Ruby and Almandine Spinel is referred for violet colour. Finally, Pleonast and Picotite are the names given for black and brown gemstone respectively.

Clarity

This bright coloured stone possesses vitreous luster and occurs in massive forms. It is found in transparent to semi translucent to opaque state. Transparent stones are usually clean and allow the light to pass through it easily. Eye clean or crystal clear gems are also available. Included crystals are quite common in opaque stones. Fractures are present in translucent gemstones but are not visible clearly.

Cut

As it is a well shaped crystal, it is cut brilliantly in almost all the shapes. The beauty of this stone is enhanced in cushion cut. In this cut the cutter save on worthy carat weight. Round, oval and emerald cut are preferred as a second choice.

Carat Weight

Red and blue coloured gemstone more than five carat in weight are rare and highly valuable. For finger rings and stud earrings, the intense red transparent eye clean gemstone can be procured having the carat weight between 1-2.5. Weight beyond 2.5 ctw would be difficult to obtain. Similarly, stones of small size are more easily available and can be used for making attractive necklaces with matching earrings, rings & bangles. The carat weight of all the stones put up together would go upto 25 carats. It is better to have smaller size stones in case of bright red and blue colours.

However, other colours are available in all sizes and weights. For example- pink coloured Spinel in different shades as rough is available below 10 ctw. Similarly other coloures as well can be procured easily upto the 20ctw as rough. After the initial gemstone processing the stones weighing between 4-6ctw are created. With these stones jewelry pieces can be made in attractive designs.

Price

This is certainly an affordable gemstone when the prices are compared with precious stone but when compared with other semi precious stones it is little expensive. Buyers need to pay higher price to possess one especially the red and blue colours. Moreover, these days due to rarity in occurrence its prices are increasing. The irony is that this gemstone is more rare than rubies.

The price for this gemstone is dependent on the colour, clarity, carat weight and transparency. Like any other gemstone, with the increase in the carat weight the price would also increase. Intense and bright colored transparent stone without too many flaws are priced maximum. Transparent red and blue colours are most in demand thus are costly but blue stones are very rare hence, fetch a huge price. Other colours are priced moderately.

Occurrence

It occurs as well formed crystals as octahedrons in igneous rocks, metamorphic rocks and in contact metamorphosed limestone. Spinels and Rubies are found in the same deposits containing magnesium and aluminum. First spinels are formed in the presence of both these elements. Later when magnesium is exhausted and only aluminum is left then Rubies are formed.

Source

First and foremost mine to produce this incredible gemstone is located in Myanmar (Burma) and it continues to offer fine gems till date. Beautiful blue and violet stone are procured from the second major producer Sri Lanka. Black coloured stones are mined in Thailand at Bo Ploi, Kanchanabur and Madagascar. It is also found in Pamir Mountains of Tajikistan, Ontario in Canada and New Jersey and New York in United States. Other countries are Afghanistan, Pakistan, Australia, Italy, Brazil, Sweden, Turkey, Russia, Vietnam and Tanzania.

Imitations

Laboratory created gems are sold as Spinel under different trade. Buyers tend to get confused with these synthetic gems, as they are ignorant about the naturally occurred gemstone. Many people are still unaware of the existence this amazing stone. They believe that Spinel is the name given to the synthetic red coloured stone. Thus, they have to know the fact that this is a semi precious gemstone occurring naturally and not a man made stone. Accordingly they should make the purchase.

Uses

Since the very beginning, this marvelous gemstone had been intrinsic part of Indian Jewelry. The ancients kings and queens used Spinel in their crowns, rings and other items. It was used as gemstone as well as beads. Pairing with other precious stones like diamond, pearl, sapphires and emerald was common. All the gems used to be more than 50 carats in weight.
Leaving the past and coming back to present, this fascinating gemstone is used for making lovely jewelry items. Most of the jewelry items are made from 18K yellow gold. Silver and white gold are used less as yellow gold complements the beauty of the stone more. This gemstone is very well paired with diamonds. Beads made of this stone are rarely used due to two reasons- First as the stone is rarely found these days, it is less suitable to make beads out of it. Second reason is that gemstones are preferred more over the beads to make the stunning jewelry pieces after all Spinel is one of the most valuable and treasured gemstone.

Precautions

It is very hard and durable gemstone as it rates 8 Mohs on the hardness scale. Therefore, apart from the general gemstone care no other specific precautions are required. Jewelries made using this stone can be worn daily. The stone is hard but should not be taken for granted that is general care is must.
This poorer cousin of Ruby may not be as expensive, but is equally treasured by the gem dealers and gem collectors due to its brilliant cut, spectacular colours and wonderful durability. Moreover, when same bright colour, attractive beauty and marvelous looks can be acquired in almost one-fourth price then it is definitely wise to buy the semi precious stone instead of precious stone.

Hope you agree !!!

Spinel Identification

by Erum Qureshi

A gemstone purported to be a spinel undergoes stringent tests in the lab for authenticity and grades (i.e. quality). It has distinctive characteristics and traits that a gemologist can easily identify.

image courtesy: Orbital Joe
The mineral spinel produces a lovely suite of gemstones which are overshadowed by the more opulent ruby and sapphire. After ruby, spinel is perhaps the most beautiful of all red gems. Its colors vary from the lightest pink to a deep ‘garnet’ red. A beautiful ‘flame’ orange, magnificent cobalt-blue and a subdued blue-green are also some color varieties of this mineral.
The derivation of the name’ spinel’ is obscure; its origins lie probably in the Latin ‘spina’, meaning thorn. It may also be derived from the Greek word, meaning spark, so christened because of its fiery red color.

Species

Spinel is a gem species by itself and is an aluminate of magnesium. Other members of the spinel group are Gahnospinel, (dark green), Gahnite (blue, dark blue), Hercynite (dark to black), Ceylonite or pleonaste (dark colors), Picotite (dark green to black) and Galaxite (dark red to black in color).

Hardness

Spinel is comparatively hard, (rating 8 on the Mohs scale of hardness). It shows an uneven cleavage and a conchoidal fracture and has a brittle nature.

Determination of Specific Gravity

Each gemstone has its own specific gravity or ratio of its weight to the same volume of water.

The specific gravity is measured by immersing the gem (spinel in this case) in a series of heavy liquids, (usually a set of three liquids of varying densities). The gem will float in a liquid of higher density, sink in a liquid of lower density and remain suspended in a liquid of the same density. Although the density/specific gravity of spinel varies from 3.58 to 3.98, gem grade spinel range from 3.58 to 3.61. Pale pink stones have much lower values.

Refractive Index

Light rays leaving one medium and entering another obliquely seem to bend a little at the place of contact. This is called refraction of light. Refractive indices for spinel are measured by placing the stone face down in a Refractometer and a reading is taken. The mineral spinel has an RI in the range of 1.712 to 1.80. However gem quality spinel will have a fairly consistent RI, steady at 1.718. In red stones rich in chromium, it may rise up to 1.74. Ceylonites have values from 1.77 to 1.80.

Absorption Spectra

The absorption spectrum of red and pink spinel is typical of stones, which owe their color to chromium. In a spectroscope, which is an instrument used to determine the wavelength of the absorbed white light when it is passed through the gemstone, the spectrum is characterized by a broad absorption in the yellow-green, and absorption in the violet. There are no lines in the blue window and faint ones in the red. The wavelength is measured in nanometers (symbol nm) or angstrom symbol ?. The absorption spectra of red spinel (in nanometers): 685, 684, 675, 665, 656, 650, 642, 632, 595-490, 465, 455. (Strong absorption lines are in bold letters; weak ones are in parenthesis.)

Fluorescence

The luminescence of spinel shows considerable variation. Natural red and pink spinel show a strong red glow under long-wave UV light, and weaker under short-wave fluorescence. Dark blue spinel are completely inert under any radiation.

Microscopic Examination

As with any other gemstone, the final call on its identification and indeed its authenticity depends heavily on its microscopic examination and the ability of the gemologist to successfully differentiate between natural inclusions and those commonly associated with synthetics. Common natural spinel inclusions include ‘spangles’ which are included crystals with surrounding iridescent stress fractures. Other common inclusions are octahedral crystals or cavities filled with calcite or dolomite. Synthetic spinel have inclusions which include gas bubbles with torpedo shapes and long parallel hose-like tubes. Most (but not all) synthetic red spinel display obvious curved growth lines which appear as broad swathes of color.