Tiger’s-eye is one of the top-selling phenomenal gems. Varying from translucent to opaque, it comes in warm earth tones that include brown, brownish yellow, and reddish brown. Its main distinguishing characteristic is its “eye,” called chatoyancy.
Tiger’s-eye’s chatoyancy is different from the chatoyancy in cat’s-eye chrysoberyl. For one thing, it usually has a wavy appearance, rather than a straight, sharp look. Also, tiger’s-eye can be cut in many ways, even flat, while cat’s-eye has to be fashioned as a cabochon to bring out the phenomenon. Explanation for these differences lies in their different “eye” causes: In tiger’s- eye, reflections of light from the fibrous structure of the gem itself create the eye, while in cat’s-eye, the eye comes from inclusions rather than structure.
Tiger’s-eye is inexpensive and available in most standard sizes. It’s a popu- lar material for cabochons (usually with flat backs), beads, tablets, cameos, and intaglios. Good toughness makes tiger’s-eye a great gem for everyday wear, and it’s a frequent choice for men’s jewelry
Other chatoyant quartz gem varieties are scarcer and usually more expensive. These include:
• Hawk’s-eye or falcon’s eye—grayish blue material with chatoyancy like tiger’s-eye
• Zebra tiger’s-eye—tiger’s-eye with grayish or blue streaks
• Cat’s-eye quartz—brownish yellow, brownish green to greenish yellow. Shows a true cat’s-eye effect. (It must be cut as a cabochon to show the eye.)
Sources
India South Africa Sri Lanka
Hardness & Toughness
Stability
Environmental Factor Reaction
Heat Sudden temperature change can cause fracturing Light Stable
Chemicals Soluble in hydrofluoric acid and ammonium fluoride; very slightly soluble in alkalis
Treatments
Treatment Purpose Stability Prevalence Detection Excellent Common
Heat Excellent Common Undetectable Dyeing Common
* If there is any doubt, send the gem to a gemological laboratory for verification.
Care and Cleaning
Type of Cleaning Advisability Ultrasonic cleaning Usually safe Steam cleaning Risky Warm, soapy water Safe
Imitations
Glass Plastic Bleaching (sometimes fol- lowed by plas- tic coating) Lightens the color. Plastic coating seals the fibrous structure and prevents con- tamination with dirt and foreign matterUndetectable, but light brown- ish yellow color is a strong indi- cation of treat- ment Produces a reddish brown color Adds various color Usually good. Some dyes may be affected by solvents, or fade with prolonged exposure to bright light. Detectable by a trained gemolo- gist or gemo- logical labora- tory*
Topaz
Most authorities agree that the name topaz comes from Topazios, the old Greek name for an island in the Red Sea, now called Zabargad. (The island never produced topaz, but it was once a source of peridot, which was con- fused with topaz before the development of modern mineralogy.) Some scholars trace the origin back to Sanskrit (an ancient language of India) and the word topas or tapaz, meaning “fire.”
The ancient Greeks believed that topaz gave them strength. In Europe during the Renaissance (the period from the 1300s to the 1600s) people thought that topaz could break magic spells and dispel anger. For centuries, many people in India have believed that topaz worn above the heart assures long life, beauty, and intelligence.
Most consumers are under the impression that topaz is an easy gem to recognize. But what they might think of as topaz could actually be the more common citrine and smoky quartz. This confusion shows when you’re displaying topaz jewelry and your customer says some- thing like “I didn’t realize topaz was so expensive” or “Isn’t topaz brown?” You will need to clear up these misunderstandings before you go further in your pre- sentation.
Topaz actually has an exceptionally wide color range that, besides brown, includes various tones and satura- tions of blue, green, yellow, orange, red, pink, and pur- ple. Colorless topaz is another option. The color vari- eties are often identified simply by hue—blue topaz, pink topaz, and so forth—but there are also a couple of special trade names:
• Imperial topaz—medium reddish orange to orange- red. This is one of the most expensive colors. • Sherry topaz—yellowish brown or brownish yellow
to orange. This term comes from the color of sherry wine. (Stones in this color range are often called precious topaz to help distinguish them from the
Strong output from sources around the world and treatments that expand the range of usable gems guarantee a steady supply of topaz. However, market availability varies according to color. Blue topaz is abundant, and there’s usually plenty of sherry topaz, but the supply of imperial, red, purple, and pink tends to be limited.
Most colors are available in standard faceted shapes, but the sizes differ from color to color. Blue usually ranges from 1 ct. to 25 cts., while other colors normally run from 1 ct. to 10 cts. You might also find some larger stones, especially in sherry or blue.
Generally, red is the most valuable topaz color, but market prices and preferences vary from country to country. Imperial topaz brings highest prices in Japan and Germany. Japanese buyers also favor pink topaz. The biggest market for blue topaz is in the US, where it pro- vides a gem alternative that’s lower in cost and more intense in color than aquamarine.
The biggest faceted gem (by weight) ever recorded is a topaz in the collection of the Smithsonian Institution. Named the “American Golden,” it’s a light yellow stone that weighs 22,982 cts. (4.60 kg or 10.14 lb.) and measures 17.3 cm ˘ 14.9 cm ˘ 9.2 cm (6.7 in. ˘ 5.8 in. ˘ 3.6 in.).
Today, topaz is one of the US birthstones for November. (The other is citrine.) Topaz is a hard stone, but it can develop cleavage. Keep this in mind when you’re showing jewelry, and advise customers to be a little extra careful when wearing this gem.
Sources
Australia Brazil Madagascar Mexico Myanmar (Burma) Namibia Nigeria Pakistan Sri Lanka United StatesHardness & Toughness
Hardness 8 on Mohs scale Toughness Poor due to cleavage
Stability
Environmental Factor Reaction
Heat High heat can alter color; sudden temperature change can cause breaks
Light Generally stable, but some brown stones fade Chemicals Affected very slightly
Treatments
Treatment Purpose Stability Prevalence Detection Heat Stable Common
Stable
* If there is any doubt, send the gem to a gemological laboratory for verification. Changes some yellow, orange, or brown mate- rial to pink Undetectable, but usually assumed because of prevalence Irradiation fol-
lowed by heat Produces vari-ous shades of blue from color- less material Routine (almost all medium to dark blue topaz is produced by treatment) Usually unde- tectable, but assumed because of prevalence. Occasionally detectable by a gemological laboratory. Caution: May very rarely be dangerously radioactive* Bue topaz
Care and Cleaning
Type of Cleaning Advisability Ultrasonic cleaning Never
Steam cleaning Never Warm, soapy water Safe