Topaz

Topaz is one of November’s birthstones (citrine is the other), but it is not as well known as many other birthstones. This may possibly be because many people think of drab yellow or brown hues when they think of topaz. I hope to remedy that misconception here, not least of all because it’s MY birthstone!

GENERAL INFORMATION:
Topaz has the chemical formula Al2(F,OH)2SiO4 and grows in long prismatic crystals. Well formed crystals often show a characteristic “chisel point”.  Although topaz is one of the hardest gemstones at 8 on the Moh’s Scale of Mineral Hardness, it is not very tough and is susceptible to breakage from impact or temperature changes. It’s best used in earrings and necklaces and should be worn in protective settings such as bezels when used for rings.

Topaz is found in many countries including the United States, China, India, Myanmar, Russia, Sri Lanka, and Vietnam.  Commercial mining areas include Brazil, Madagascar, Namibia, and Pakistan.

Topaz_crystal_a

Topaz crystal from Utah showing “chisel point” termination.  Photo (c) J. Fenton, 2017

COLOR:
Besides yellow and brown, topaz occurs naturally in orange, pink, purple, red, light blue and light green as well as colorless crystals.  Orangey-red to pink gems may be called Imperial Topaz and are among the most valuable colors.

Sap_top_b

Sapphire and blue topaz necklace. Photo (c) J. Fenton, 2017

TREATMENTS:
Blue topaz: Prior to researching this article, I was unaware of naturally occurring blue topaz. It’s quite rare and most blue topaz found in jewelry comes from colorless material that has been irradiated and heated.  There are several methods of treatment; for more information read this article.  The combination of heat and irradiation results in a range of blue colors; “Swiss blue” and “London blue” are two common trade names.  The treatment is stable and permanent.

Mystic topaz: Colorless topaz is enhanced with a thin covering of an iridescent film.  This gives the gem a beautiful display of different colors as you move it in the light. The treatment is not permanent; the film can be scratched or polished off.  Care should be taken to avoid abrasion to the surface when wearing this gem.

CARE:
Clean your topaz jewelry in warm soapy water; don’t use steamers or ultrasonic cleaners.

References:
https://www.gia.edu/topaz
http://4cs.gia.edu/en-us/blog/november-birthstone-topaz-and-citrine/
https://www.gemselect.com/gem-info/mystic-topaz/mystic-topaz-info.php
https://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness
Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s