|Unusual Star Garnet
Star garnet is an unusual form of garnet. Asterism, or the star effect,is associated mostly with star sapphire and star ruby. But in fact a small of group of other gemstones can also exhibit this effect, though specimens are fairly rare. The other star gems include moonstone, quartz, spinel, citrine, diopside, emerald, chrysoberyl and garnet.
Star garnets are so rare that thus far they have only been found in two places in the world: in the state of Idaho in the USA, and in India. The garnet varieties that occasionally exhibit asterism are almandine and a mixture of almandine and pyrope garnet.
Star garnets are usually opaque and colored a deep brownish red or a reddish black. Like all star gems, the star effect is caused by inclusions of rutile. But in order to display the star effect the rutile needles must have the right alignment to reflect light in a pattern forming a mult-ray star.
Most star garnets display a 4-ray star, but 6-ray stars are sometimes seen. Some dealers claim that only the Idaho star garnets ever display a 6-ray star, but this claim is difficult to prove since specimens with a 6-ray star are very rare.
Idaho is so proud of their star garnet deposits that they named star garnet the state gemstone. Star garnets are mined in northern Idaho in a region a northeast of Moscow and southeast of Couer D'Alene.
The star effect in most star garnets is subtle and requires the correct lighting to see the star clearly. The best lighting is bright sunlight in the middle of the day where the sun is directly overhead. Using a focussed light like a narrow beam halogen spotlight or a small flashlight that can be focussed to a narrow beam will also work. Then stand directly above the stone and look straight down to see the star.
- First Published: August-15-2008
- Last Updated: October-06-2010
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