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Introduction:
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While there has been much debate about the best source for Alexandrite, the uniqueness and relatively short history of the color-change variety of chrysoberyl has made it one of the most coveted gems to collectors and connoisseurs alike. Although very rare, Alexandrite is available in a wide range of qualities, but mostly in sizes around 1 carat or less. Availability has increased since the 1987 find in Minais Gerais, Brazil, and it has been estimated that by 1990 some 5,000 to 10,000 carats of Brazilian Alexandrite had been cut and brought to market. This is quite a large quantity for such a rare stone. The debate over Russian and Brazilian Alexandrite has dominated much of the press throuhgout the stone's short history, and it is known that some dealers are very one sided about the origin of their Alexandrites. Sri Lanka is also well known for its supply of Alexandrites and produces quite a large sum of the total available. |
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History
of...
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Named as a tribute to Czar Alexander II of Russia, Alexandrite was a prized gem among the Russian aristocracy. Alexandrite was found on his birthday in May of 1830 in the Ural Mountains of Russia and was held in high regard due to it's color similarities to its host country's military colors, green and red. It is reported that nearly all Russian Alexandrite was mined during the 19th century and is the most highly coveted of all Russian gemstones. Just as supply was beginning to be depleted on Russian material, large deposits were found in Sri Lanka (what was then called Ceylon). Finally, Brazil became a large contributor to the world supply of Alexandrites and the debates over what region supplies the best material began. Some dealers around the world were purists and prefered only the Russian material. It is known that Russian stones are referred to as having Siberian colors. Alexandrites color change between deep greens and dark reds are what is desired in an Alexandrite and can be found in both Russian, Sri Lankan and Brazilian stones. Generally it is found that in larger sizes, meaning closer to 10 carats, the Sri Lankan material carries the strongest of colors. However, Russian and Brazilian stones rank among the best available in the world. Today, most dealers accept all origins of Alexandrite and find that good material is available because of the newer Brazillian find.
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Technical
Specifications:
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| DESCRIPTION |
| Alexandrite is the color change variety of the mineral chrysoberyl. |
| Chemical
Composition: |
BeAl2O4 |
| Appearance: |
•Transparent •Daylight shows yellowish, brownish, grayish or bluish green; incandescent light shows orangy or brownish red to purple-red •Changes color based on light source and may also show chatoyancy |
| Misnomers: |
None known |
| Typical
Sizes: |
Melee sizes to 5 ct; faceted stones as large as 60 ct are known |
| Cut Styles: |
Faceted and cabachon |
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| IDENTIFICATION |
| Optic
Character: |
DR, biaxial positive |
| Refractive
Index: |
1.746-1.755 (+ .004, - .006) |
| Birefingence: |
.008 to .010 |
| Dispersion: |
.015 |
| Pleochroism: |
Strong, green, orange, and purple-red |
| Ultraviolet
Fluorescence: |
Inert to moderate red (LW and SW) |
| Absorption
Spectra: |
Two strong lines at 680.5 and 678.5 nm and weak lines at 665, 655, and 645 nm, partial absorption between 580 and 630, three weak lines at 476.5, 473, and 468 nm, and general absorption in the violet. |
| Cause
of Color: |
Chromium |
| Specific
Gravity: |
3.73 (+/- .02) |
| Polish
Luster: |
Vitreous to subadamantine |
| Fracture: |
Conchoidal |
| Luster: |
Vitreous to greasy |
| Cleavage: |
None |
| Indentifying
Characteristics: |
Fingerprint inclusions, silk, color change |
| Known
Enhancements: |
None |
| DURABILITY RATINGS |
| Hardness: |
8 1/2 |
| Toughness: |
Excellent |
| Alexandrite is sometimes mistaken for natural and synthetic corundum, natural and synthetic spinel, synthetic alexandrite, andalusite and pyrope garnet. There are also doublets available that could be mistaken for alexandrite. They may have good color change containing red garnet on top and red glass on bottom. |
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Care
Tips:
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| Alexandrite is a tough and stable stone, and most care and cleaning methods are typically safe. |
| Cleaning Methods |
| •Ultrasonic: |
Usually safe |
| •Steamer: |
Usually safe |
| •Warm
soapy water: |
Safe |
| Stability of Stone |
| •Heat
tolerance: |
Stable |
| •Light
tolerance: |
Stable |
| •Chemical tolerance: |
None |
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Recommended
Uses:
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Rings
- Due to the durability and uniqueness of alexandrite it is most often used as a center stone for a ring. Expect to pay a little more for this hard to find stone, and it is recommended to protect the investment with a platinum mounting. Mix platinum and diamonds with a center stone alexandrite and heads will turn. Earrings
- Because alexandrite is a rare stone, it is not recommended for use in earrings. If, however, a pair of earrings is desired, it is recommended to use a smaller pair of matching stones. It will be dificult to find a matched pair of alexandrites and is more likely to be available in smaller size rounds. Earrings are also easily lost or misplaced and cost should be of concern when considering alexandrite for earrings.
Pendants - Pendants are usually made with larger stones or pearls and are not necessarily the best choice for alexandrite. Since availability is greater in 1 carat or less sizes an alexandrite pendant would look best if mixed with other stones such as diamonds. A three stone pendant with an alexandrite and diamonds would be unique and quite beautiful to alexandrite admirers.
Bracelet - Not a recommended choice due to cost and availability. Bracelets generally consist of many matching stones and it will be extremely difficult, if at all possible, to find a quantity of matching alexandrites.
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Source
Map:
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| All technical specifications and care
tips on this page was referrenced from the "Gem
Reference Guide" published by the Gemological Institute
of America |
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