Topaz is a popular and durable gem, occurring in a wide range of colors. Although topaz is frequently associated with a golden yellow color, it can be found in a variety of colors. The rarest are natural pink, red, and fine golden orange, sometimes with a pink tone. Traditionally, all yellow, brown, and orange colored transparent gems were called topaz. With the advent of modern gemology, many of these stones were re-classified as different species (particularly quartz).
Clarity and size have a significant effect on the value of topaz. The highest values go to the rare pink and red stones, then orange and yellow. Intense, reddish orange topaz is sometimes called "Imperial Topaz." Yellow, orange, and brown stones are somewhat common. Colorless topazes are common and are low-value gems in any size.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Varieties||Imperial Topaz, Mystic Topaz|
|Crystallography||Orthorhombic. Crystals prismatic, stumpy, sometimes very large, often well formed; also massive, granular, as rolled pebbles.|
|Colors||Colorless, white, gray, pale to medium blue, greenish, yellow, yellow-brown, orange, pale pink, deep pink, tan, beige, red.|
|Specific Gravity||There is a rough correlation between color and density, as follows: pink: 3.50-3.53; yellow: 3.51-3.54; colorless: 3.56-3.57; blue: 3.56-3.57. See "Identifying Characteristics" below.|
|Birefringence||See "Identifying Characteristics" below.|
|Cleavage||Perfect basal (1 direction). Brittle.|
|Luminescence||Blue and colorless: weak yellow-green in LW, weaker in SW, greenish white to violet-blue in X-rays, and gems turn brown due to irradiation. Sherry brown and pink: orange-yellow in LW, weaker in SW, sometimes greenish white in SW. This material fluoresces brownish yellow to orange in X-rays.|
|Spectral||Heat treated pink gems contain Cr and may show a Cr spectrum with a weak line at 6820. As in ruby, this line may reverse and become fluorescent. Otherwise, not diagnostic.|
|Enhancements||Pink or red, may be heat treated. Most blue topaz has been irradiated and heat treated.|
|Transparency||Transparent to Opaque|
|Formula||Al2SiO4(F,OH)2 + Cr.|
|Pleochroism||Varies with color of material:|
|Optics||RI: 1.609-1.643; biaxial (+). See "Identifying Characteristics" below.|
|Etymology||From the Sanskrit tapas for fire, alluding to the orange color, or from Topazos, an ancient Greek name for St. John's Island in the Red Sea where the gem was said to be mined.|
|Occurrence||In pegmatites and high temperature quartz veins; also in cavities in granite and rhyolite; in contact zones; in alluvial deposits as pebbles.|
|Inclusions||Usually planes of two or more non-miscible liquids, each containing a gas bubble. Two and three-phase inclusions have also been noted.|
The specific gravity and optical properties of topaz vary by stone color.
|bluish pale yellow|
|Ouro Preto, Brazil|
|brownish||rich in (OH), Cr|
|Thomas Range, Utah|
|Tarryall Mountains, Colorado|
|Schneckenstein, Saxony Germany|
While topaz has been created in the lab, it is not usually commercially available.
In the 1960s, a two-step method was discovered to turn colorless topaz blue. First, the rough is irradiated, turning it brown. Then, the brown stone is heated to achieve a stable, blue color. The process so nearly duplicates what happens in the Earth, a treated stone cannot be distinguished from a natural. Prior to this development, natural light blue topaz was rare and valuable. Colorless topaz was common and could be purchased cheaply per ton. The aftermath: prices for blue topaz fell, and these are now among the least expensive gems available.
Topaz that has undergone this treatment and been turned dark blue is sometimes used as a simulant for aquamarine. These are distinct gem species. However, since topaz is typically less expensive than aquamarine, consumers should be wary of unscrupulous vendors who may try to sell treated topaz as aquamarine.
Heat treatments are also used to change some yellow, orange, and brown topaz to pink or red. This procedure is common, stable, and undetectable.
A diffusion treatment is used to create mystic topaz, a stone with a multicolored coating on its surface. This is a common procedure. The surface coating can easily be scratched. This treatment can be detected by immersion.
- New Hampshire: crystals.
- Texas: colorless and blue, some facetable to large size.
- Pike’s Peak area, Colorado: fine blue crystals in granitic rocks; also colorless, reddish, yellow, some facetable.
- Thomas Range, Utah: sherry-colored terminated crystals in rhyolite; facetable.
- Minas Gerais, Brazil: fine yellow to orange crystals, facetable to large size: also colorless and pale yellow crystals up to several hundred pounds in size, mostly transparent; pale blue crystals and rolled pebbles, much facetable; some orange crystals contain Cr and when heated (burned) turn pink and show a Cr spectrum. Such material may be distinctly reddish even before heating.
- Mardan, Pakistan: fine pink crystals, terminated, cuttable, in limestone matrix, at Ghundao Hill, near Katlang.
- San Luis Potosi, Mexico: fine brownish to sherry-colored crystals; also colorless, many excellent forms, cuttable, some yellowish: can be darkened by irradiation but color fades in sunlight.
- The Urals, Russia: fine blue crystals, often cuttable; also green, magenta colors (gemmy) and pinks from Sanarka.
- Jos, Nigeria: fine blue crystals, also white, many cuttable.
- Madagascar: various colors in crystals and pebbles, often cuttable.
- Sri Lanka and Myanmar: from the gem gravels, colorless, yellow, and blue gemmy masses.
- Queensland and Tasmania, Australia: blue, colorless and brownish gem crystals.
- Tingha, New South Wales, Australia: green. gemmy.
- Klein Spitzkopje, Namibia: colorless and blue crystals from pegmatites, gemmy.
- Zimbabwe; Cornwall, England: Scotland; Japan: crystals and pebbles.
- Schneckenstein, Germany: faint yellow, gemmy.
Topaz crystals may weigh hundreds of pounds and are often quite gemmy at this size. Gems up to 20,000 carats have been cut from material of various colors. Museums seem to delight in obtaining monster-sized topaz gems for display. Pink gems over 5 carats (Pakistan) are rare, however, and a Brazilian deep orange gem weighing more than 20 carats is considered large.
The largest known pink topaz is an oval of 79+ carats from Russia. The largest Brazilian topaz crystal ever found of an orange color reportedly measured 5 x 27 cm and weighed nearly 2 kg. A very fine lot (9 cuttable crystals) found in the 1960s weighed over 900 grams and yielded several superb gems, one weighing more than 100 carats and several over 50 carats.
Giant topazes exist in blue, colorless, and pale yellow colors. Red topaz from the tips of some Brazilian crystals is exceedingly rare, the largest about 70 carats.
- Smithsonian Institution (Washington, D.C): 7725 (yellow, Brazil); 3273 (blue, Brazil); 2680 (colorless, Brazil); 1469 (yellow-green, Brazil); 1300 (sherry, Brazil); 685 (pale blue, Brazil); 398 (pale blue, Russia); 325 (colorless, Colorado); 170.8 (champagne, Madagascar); 146.4 (pale blue, Texas); 93.6 (orange, Brazil); 50.8 (colorless, Japan); 34 (deep pink, Brazil); 24.4 (blue, New Hampshire); 17 (blue, California).
- American Museum of Natural History (New York): 71 (red, Brazil); 308 (pale blue, Brazil); 258 (deep blue, Brazil); 1463 (deep blue, egg-shaped, Brazil); 241 (pale orange-brown, Burma).
- Natural History Museum (London, UK): 137 pounds (crystal, Norway); 1300 (colorless, Brazil); 614 (blue, Brazil).
- Royal Ontario Museum (Toronto, Ontario, Canada): 3000 (blue, Brazil); 365 (pale brown. Burma).
- Los Angeles County Museum (Los Angeles): 1800 grams (orange crystal, Brazil).
- National Museums of Canada (Ottawa, Ontario): 498.61 (light blue, untreated, Brazil).
- Private Collection: 173 (blue, Texas); 7,033 (dark blue. treated); 21.327 (light blue, treated, emerald-cut, reputedly the world‘s largest faceted gemstone called The Brazilian Princess): ~79 (pink oval, Russia, world’s largest this color but not flawless); 58.8 (pink oval. Russia, flawless).
- Sky Blue, light blue
- Swiss Blue, medium blue
- London Blue, dark blue
- Mystic, diffusion treated topaz showing multiple colors
- Hyacinth, dark orange to orange red
- Imperial topaz, highly saturated medium, reddish orange
- Precious, refers to high value topaz
- Sherry, brownish yellow to orange or yellow brown
- White, colorless