|Moldavite and Tektite
Moldavite is a bottle-green to brown-green gemstone belonging to the tektite group. It has garnered attention due to its unusual origin - it is thought to have formed from condensed rock vapors after a meteorite impact. You will sometimes see moldavite touted as "the only known extraterrestrial gemstone on earth" or "the gemstone from the stars".
Tektite is the general term used to refer to natural glass rocks formed by the impact of large meteorites on the Earth's surface. They are found in just four locations around the world, known as strewnfields. Material from a large meteorite impact may be strewn several hundred kilometers from the impact crater. The four known strewnfields are centered in Germany, Australia, the USA (Chesapeake Bay, Maryland) and Ghana. Moldavite has been found only in the Czech Republic, part of the German strewnfield.
Though moldavite has been promoted by some as extraterrestrial, that is probably not the case. According to tektite theory, a meteorite impact melts material from the Earth's surface and catapults it up to several hundred kilometers away from the impact site. The molten material cools and solidifies to glass. According to this theory, a meteorite impact causes the formation, but the precursor material of tektites is primarily of terrestrial origin, as determined from isotopic measurements. Today, the terrestrial origin of tektites is widely accepted based on the results of geochemical and isotopic studies.
Moldavite gets its name from the town of Moldauthein in the Czech Republic where it was first found. There are currently four moldavite mines operating in the Czech Republic, but it is estimated that the supply of gem-grade material will be exhausted in about ten years' time.
Moldavite is composed of silicon dioxide and aluminum oxide. As a natural glass, similar to obsidian, it has no crystal structure. It has a hardness of about 5.5 on the Mohs scale, and a density of 2.32 to 2.38, similar to obsidian. Moldavite has a refractive index of 1.48-1.54, also similar to obsidian and a vitreous luster.
- First Published: January-18-2010
- Last Updated: September-08-2014
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