Topaz

What is topaz made of? The fluorine check, worked

The names. The September 2026 IMA-CNMNC Master List has one topaz row, Al2SiO4F2, status G, grandfathered, with the year printed as ? and the country as unknown; a script over the list finds no other row whose formula begins Al2SiO4. The Handbook sheet writes Al2SiO4(F,OH)2: the same mineral, with the sheet allowing hydroxyl in the fluorine site.

The arithmetic, on standard atomic weights (Al 26.9815, Si 28.085, O 15.999, F 18.998, H 1.008). Al2SiO4F2 has a formula mass of 184.04 and is 20.65% fluorine, 29.32% aluminium. Thomas Range, Utah, the sheet’s first analysis, reads F 20.37%; scaled to three silicon plus aluminium it gives 1.97 fluorine and 0.04 hydroxyl, matching the formula printed under it. That is the control. The Brewer mine, Chesterfield Co., South Carolina analysis reads F 13.23% and H2O+ 2.67%: 1.26 fluorine and 0.53 hydroxyl, so fluorine is 70% of the pair.

What the check shows. Even the sheet’s low-fluorine example, from a 1937 paper titled Massive low-fluorine topaz from the Brewer mine, is fluorine-dominant and so fits the IMA’s Al2SiO4F2. The two analyses fall well short of a hydroxyl-dominant composition, and this page names no species for one. The sheet’s Occurrence field explains the fluorine: veins and cavities in granite, pegmatite and rhyolite, and greisen, from high-temperature, volatile-rich fluids, with fluorite and cassiterite among the associates.

Is topaz a quartz? The 14.27 g floor

No: topaz is Al2SiO4F2, hardness 8, density 3.49 to 3.57; quartz is SiO2, hardness 7, density 2.65. The rule: weigh a clean 20.00 g piece in air, then suspended in water. Topaz reads 14.27 to 14.40 g; quartz, citrine and smoky quartz alike read 12.45 g, as on the live quartz page. Below 14.27 g, it is not topaz. The method and its error sources are on how to measure specific gravity at home.

Why the question is asked. The International Gem Society topaz article says citrines are sometimes misidentified as topaz because of the long association with yellow, and lists smoky topaz, Brazilian topaz and Madeira topaz as erroneous names for smoky quartz. GIA notes the reverse: brown topaz is sometimes mistakenly called smoky quartz. The sheet’s Name field adds an older confusion: topazion was long the name for the Red Sea island of Zabargad, known for olivine, which was referred to since antiquity as topaz; see olivine.

Documented failures of the floor. Spinel reads 14.44 g at GIA’s specific gravity 3.60, just above topaz. Glass, which the gem society gives 2.30 to 4.50, spans 11.30 to 15.56 g. So the floor rules things out; it does not prove topaz. Cleavage can help on rough: topaz has one perfect cleavage, on {001}, read from the rendered sheet, where quartz’s is rarely observable. Citrine’s own questions, including heat treatment, are on how to tell if citrine is real.

Blue, mystic and imperial topaz: what GIA and the gem society say

Blue. GIA writes that topaz’s blue colour is hardly ever natural and is almost always caused by treatment; colourless topaz is plentiful and often treated to blue. Its quality-factor page says treaters use a combination of radiation and heat, and that treatment has brought blue topaz to a broad market since the 1970s. The gem society describes the two steps, irradiation to brown and then heating to a stable blue, and says the result cannot be distinguished from natural blue. This page gives no test for it, because the sources give none.

Mystic. The gem society says mystic topaz is made by chemical vapour deposition, a multicoloured coating on the surface that can easily be scratched, and that the treatment can be detected by immersion. It also notes that dark blue treated topaz is sometimes used as a simulant for aquamarine; that question is on how to tell if aquamarine is real.

Imperial and precious. GIA calls imperial topaz a medium reddish orange to orange-red and says commercial deposits are, so far, found in a single area, Ouro Prêto in Brazil. It gives sherry topaz as yellowish brown or brownish yellow to orange, and says stones in that range are often called precious topaz to distinguish them from citrine and smoky quartz. GIA attributes natural pink, red and violet-to-purple topaz to chromium, and yellow, brown and blue to imperfections at the atomic level.

Where topaz is found: Ouro Preto, the Urals, Thomas Range and Schneckenstein

The Distribution field opens widespread; only a few localities for the finest specimens can be mentioned and names: near Mursinka, Ural Mountains, and the Adun-Chilon and Borshchovochnoii Mountains, Siberia; Schneckenstein, Saxony, Germany; Xilingeleimeng, Inner Mongolia; Ghundao Hill near Katlang, and the Skardu and Gilgit districts, Pakistan; the Mogok district, Myanmar; Tanokamiyama and the Naegi district, Japan; Ouro Preto and near Virgem da Lapa, Minas Gerais, Brazil; Tepetate, San Luis Potosí, Mexico; the St. Anne’s mine, Zimbabwe; Alto Ligonha, Mozambique; Klein Spitzkopje, Namibia; and the Jos district, Nigeria.

In the USA it names Devils Head, Colorado; the Thomas Range, Utah; Lord’s Hill, Maine; Baldface Mountain, New Hampshire; Ramona, California; and near Streeter, Texas. It names no British locality, and we add none. Crystals reach 1.2 m on the sheet; GIA reports a transparent crystal from Minas Gerais weighing 596 pounds.

Its company on the Association line: tourmaline, beryl, microcline, albite, fluorite, cassiterite, zinnwaldite, quartz. Beryl’s hardness comparison against topaz is on beryl, and the pegmatite tourmalines on tourmaline. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.

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