An apatite crystal appears to float, suspended over a rutile silk cloud in a star sapphire.
An apatite crystal is suspended over a cloud of rutile silk in this untreated star sapphire. Photomicrograph by E. Billie Hughes; field of view 6 mm.
One of the beauties of working with gemstones is that each time you peer into a stone, you get a glimpse of the universe held within. When we first examined the scene in a star sapphire (see above), we were delighted with the view. A feature that immediately stands out is the triangular crystal, which displays terraced growth features and iridescence on the surface when illuminated with a fiber-optic light. Analysis with micro Raman revealed that this crystal is apatite.
What makes the scene even more stunning is the way the crystal seems to float over a cloud of rutile silk. This same silk is what creates asterism in the stone.
While in this case the apatite crystal resides in a sapphire from Sri Lanka, apatite has also been reported in corundum from a variety of sources, including Afghanistan, Cambodia, Madagascar, Myanmar, Nigeria, Pakistan, Tanzania, Thailand, the United States, and Vietnam.
Apatite can be found not only in ruby and sapphire from different origins, but also in many other types of gems. In our laboratory, we have encountered apatite inclusions in emerald, spinel, and garnet.
Apatite is a relatively common mineral, so it is not surprising to find it so often as an inclusion. Although it may occur frequently, in this instance it is anything but mundane.
About the Author
E. Billie Hughes visited her first gem mine (in Thailand) at age two and by age four had visited three major sapphire localities in Montana. A 2011 graduate of UCLA, she qualified as a Fellow of the Gemmological Association of Great Britain (FGA) in 2013. An award winning photographer and photomicrographer, she has won prizes in the Nikon Small World and Gem-A competitions, among others. Her writing and images have been featured in books, magazines, and online by Forbes, Vogue, National Geographic, and more. In 2019 the Accredited Gemologists Association awarded her their Gemological Research Grant. Billie is a sought-after lecturer and has spoken around the world to groups including Cartier and Van Cleef & Arpels. In 2020 Van Cleef & Arpels’ L’École School of Jewellery Arts staged exhibitions of her photomicrographs in Paris and Hong Kong.
Notes
This article first appeared in Gems & Gemology, Fall 2021, Vol. 57, No.3, p. 268.