When is an imperfection desirable? From the “beauty spots” of vintage Hollywood starlets (think Elizabeth Taylor’s tiny mole) to Barbra Streisand’s famously crooked nose, sometimes a flaw can be memorable. And so it is with gemstones. In previous posts, I have shown some rutiles of golden titanium & tourmaline that can be found in in quartz, but the most precious & famous desirable flaw is probably the “horsehair” inclusions found in some demantoid garnets. The inclusions are actually needles of chrysotile (a form of asbestos), which radiate outwards from a tiny crystal & can sometimes appear similar to the finer rutile needles in quartz. In reality, these are usually too small to be appreciated without magnification, both because the inclusions are tiny, but also because demantoid garnets are generally small stones (cut stones over 2 carats are very rare). With 10x magnification, this is what you might see.
In the case of the demantoids, the inclusions reflect the light and make the stone appear to glow. Only demantoids from Russia have the horsetail inclusion; stones from Namibia are free of them and considered much less valuable. Good color stones with horsetail inclusions often cost $1000-2000/carat for stones under 1/4 carat & the price goes way up from there. If you are offered demantoid garnet for sale, be sure to look at the stones carefully with a jeweler’s loupe to confirm the inclusions before purchasing.
Next week–more fabulous flaws.