Topaz
Current inventory:  0 gems
 

  
Topaz has been know since antiquity and named from the Greek topazion, meaning to seek, apparently in allusion to the Island of Zabargad (Zabirget or St. Johns), in the Red Sea, Egypt; the location of which was long hidden.

Discovered in prehistory; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Al₂SiO₄(F,OH)₃  

Aluminim Silicate Fluoride Hydroxide

Molecular Weight:

182.25 gm

Composition:

Aluminum

29.61 %

Al

55.95 %

Al₂O₃

Silicon

15.41 %

Si

32.97 %

SiO₂

Hydrogen

0.50 %

H

4.45 %

H₂O

Oxygen

43.02 %

O

Fluorine

11.47 %

F

11.47 %

F

-  %

F

-4.83 %

-O=F₂

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/B.02-70

Nickel-Strunz 10th Ed. ID:

9.AF.35

9 : SILICATES (Germanates)
A : Nesosilicates
F : Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination

Related to:

n/a

Varieties:

Imperial Topaz, Pyknite

Color Variety Names:

Champagne, Imperial, London Blue, Mystic, Sky Blue, Swiss Blue,

Synonyms:

Chrysolithos, Colorado Topaz, Physalite, Pyrophysalite, Silver Topaz, White Topaz

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Well-formed crystals common, typically morphologically complex, long to short prismatic, to 1.2 m. Prism faces commonly vertically striated, with etch and growth figures on non-prism faces; columnar, compact, massive.

Twinning:

None

Physical Properties

Cleavage:

Perfect on {001}

Fracture:

Subconchoidal to Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

8.0

Density:

3.49 - 3.57 (g/cm³)

Luminescence:

Rarely Fluorescent; blue and colorless gems: weak yellow-green in LW UV, weaker in SW UV; sherry brown and pink gems: orange-yellow in LW UV, weaker in SW UV, sometimes greenish white in SW UV.

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colourless, white, pale blue, light green, yellow, yellowish brown, pink, red

Transparency:

Transparent to Opaque with inclusions

Luster:

Vitreous

Refractive Index:

1.606 - 1.644  Biaxial ( + )

Birefringence:

0.0090 - 0.0110

Dispersion:

Noticable; 0.0140; r > v

Pleochroism:

Weak; X = yellow; Y = yellow, violet, reddish; Z = violet, bluish, yellow, pink

Occurances

Geological Setting:

In veins and cavities in granite, granite pegmatite, rhyolite, and in greisen, formed from high-temperature, volatile-rich pneumatolytic hydrothermal fluids. From high-grade metamorphism of aluminous, quartz-rich, and fluorine-bearing sediments. As a heavy detrital mineral.

Common Associations:

Albite, Beryl, Cassiterite, Fluorite, Microcline, Quartz, Tourmaline, Zinnwaldite

Common Impurities:

None

Type Locality:

None (prehistoric)

Year Discovered:

Prehistoric

View mineral photos:

Topaz Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Topaz is an abundant and popular gem available in a wide variety of colors. Natural colors include colorless, pale to medium blue, pale greenish, yellow, golden brown, beige, champagne, orange, pale to deep pink and, rarely, red. Many other colors, including the popular deep blue, have been created by heating and irradiating Topaz. These colors have been given commercial names such as London Blue, Swiss Blue and Sky Blue. Treated Topaz is also available in shades of green from Teal Green to Emerald Green. Another Topaz treatment is to put a very thin titanium coating on the pavillion of a faceted gem resulting in a rainbow of colors. This gem goes by the commercial name of Mystic Topaz.

Very large Topaz crystals have been found weighing hundreds of pounds. These crystals are often very gemmy and have produced faceted gems of up to 20,000 carats! Possibly the largest faceted gemstone in the world is a light blue Topaz (treated) from Brazil weighing 21,327 carats cut in an emerald shape called the Brazilian Princess. Many of the other colors of natural Topaz (yellow, orange, pink, red) are found as much smaller crystals. Natural orange Topaz is oftern called "Imperial" or "Precious" Topaz.

There are many locations worldwide where Topaz can be found. A few locations for the finest specimens include near Mursinka, Ural Mountains, Russia; the Skardu and Gilgit districts, Pakistan; the Mogok district, Myanmar (Burma); Ouro Preto, Minas Gerais, Brazil; Tepetate, San Luis Potosi, Mexico; and in the USA at Ramona, San Diego County, California; Devils Head, Douglas County, Colorado; the Thomas Range, Juab County, Utah, USA.
 

  
Topaz gems for sale:

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