Blue topaz

Blue topaz is topaz that is blue. Naturally blue topaz exists, but it is mostly very pale; according to GIA, the blue of topaz on the market is hardly ever natural. Colourless topaz is plentiful: it is first irradiated, which turns it brown, and then heated to a stable blue. The trade calls the light shades “Sky Blue”, the medium shades “Swiss Blue” and the dark shades “London Blue”. Once the treatment spread in the late 1970s, blue topaz became both the favourite colour of topaz and one of the least expensive gems.

Not on the official lists. The current US list used by jewellers gives turquoise, zircon and tanzanite for December, while topaz is the birthstone for November. Some jewellery websites nevertheless include blue topaz among the December stones.

Jewellery: hard, brilliant and inexpensive, it is widely used in rings, earrings, necklaces and bracelets. It is often cut to standard sizes and set in multi-stone and mass-market jewellery. An alternative to aquamarine: light blue topaz looks like aquamarine and costs much less, so it is chosen in its place; but which stone it is must be stated clearly at sale. Large stones and carvings: because it is easy to find in large sizes, it suits big cut stones and carvings. Collecting: naturally blue topaz crystals from places such as Ukraine, Zimbabwe and the Urals are sought by collectors.

It has a hardness of 8 on the Mohs scale. It scratches glass and steel; a steel knife cannot scratch it. Its specific gravity is 3.56–3.57 g/cm³.

Its best-known localities: Mason County, Llano Uplift, Texas, USA; Volyn deposit, Khoroshiv (formerly Volodarsk-Volynskyi), Zhytomyr Oblast, Ukraine; Central Urals pegmatites (Murzinka area), Sverdlovsk Oblast, Russia; St. Ann's mine, Miami (Mwami) district, Mashonaland West, Zimbabwe; Pikes Peak area, Colorado, USA.

As a topaz it is hard (8) and scratches glass and quartz. But it has perfect cleavage, so a hard knock can split it along a smooth plane. It is most often confused with aquamarine. Blue topaz has a clearly higher refractive index (about 1.61–1.62) and specific gravity (about 3.56) than aquamarine (about 1.58 and 2.7), so a gem lab tells them apart easily. A large, clean, dark or vivid blue topaz is almost certainly treated; natural blue topaz is mostly very light blue. Routine gemmological tests usually cannot tell natural blue from treated blue with certainty. Treated stones sold as “natural blue”: irradiation and heating mimic what happens in nature so closely that routine tests usually cannot reveal the treatment. A claim of natural colour should rest on documents showing where the stone came from.

On the “street to diamond” value ladder it sits on step 5 of nine: Ornamental stone. Blue topaz is a plentiful, inexpensive gem; its value depends mostly on the shade and saturation of the colour, the size of the stone and the quality of the cut. Small stones are cheap; according to GIA, value rises for stones larger than 10 × 8 millimetres. Because blue topaz is usually clean, eye-visible inclusions lower its value. Stones coloured by coating are worth less, while naturally blue topaz with documented origin from Mason County, Texas, is valued much more highly in its home region.

Today crystal-therapy websites link blue topaz with the throat chakra and claim that it makes communication, speaking openly and self-expression easier. In Türkiye, stone sellers and crystal-therapy websites claim that blue topaz relieves stress and brings calm and peace of mind. There is no scientific evidence that blue topaz makes communication easier or relieves stress; persistent anxiety or stress calls for a doctor. The colour of blue topaz on the market does not come from nature but from irradiation in a nuclear reactor or an accelerator, followed by heating. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.

Blue topaz that has been irradiated, stored and measured at licensed facilities carries radioactivity below the legal limits by the time it is sold. In neutron-irradiated stones, trace elements temporarily become radioactive, so these stones must be stored for months and sometimes years. In the United States such stones are tested by a licensed body before sale; stones from unregulated channels carry no such assurance. Stones treated with cobalt-60 gamma rays do not become radioactive.