Moldavite Info

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General

Moldavites are green, brownish-green or brown natural glasses (Mohs scale 5.5 - 6.6), in all probability formed by a meteorite (perhaps 1.5 km in diameter) impact in southern Germany (Bavaria).
Since decades people searched for moldavites and sold them. Today moldavites become harder and harder to find, and their price might increase.
Moldavite got its name from the main strewnfield (of a meteorite impact) in Bohemia, traversed by the river Vltava (German: Moldau).
Moldavites contain more or less 80% SiO2, 10% Al2O3, 3% K2O, 2% FeO, 2% MgO, 1.5% CaO, 0.5% Na2O3 and 0.5% TiO2.

Formation

The Ries impact happened in Bavaria, the southern part of Germany, approximately 15 million years ago. The Ries meteorite had an incredible speed of about 72,000 km per hour, and produced an unbelievable energy eruption similar to the simultaneous explosion of some 100,000 a-bombs of the Hiroshima type. The crater was about 500 m deep.

The Steinheim Crater
About every sixth asteroid near the earth has a smaller companion. The "Ries meteorite" and its smaller (appr. 150 m in diameter) companion which probably caused the "Steinheim crater" (diameter: 3.8 km, 30 km southwest of the Ries crater), came, according to scientists, from southwest and hit the earth in an angle between 30° and 50°. A pressure of some million bar and temperatures up to about 30,000° let the meteorite and about 3 km3 of the surrounding rocks evaporate.
About 2 seconds after the impact of the "Ries meteorite" masses of rocks (about 150 km3) were thrown out of the crater, covering an area up to 40 km away with the ejected stones, up to 100 m (near the crater).

The Steinheim Crater *
100 km away from the impact the fireball appeared about 30x larger and 70x brighter as the sun. Within this area all kinds of life was exterminated within seconds. The shock wave had an initial speed of about 600 km per hour and circled round the earth. The roar could be heard around the world.

Moldavites belong to tektites (from Greek "tektos" = molten), natural glassy material, which has been formed by the impact of meteorites. Moldavites were created as a result of melted material which was blown out of the "Ries crater", then flew 250 - 450 km through the air in eastern / northeastern direction, then cooled and solidified, and finally hit the ground as green to brown glassy material.

Thousands of years after the impact the crater (then still 100 m deep because 400 m were filled with melted rocks and impactites like suevite) was filled with water. One estimated that the huge suevite
The Ries Crater *
layer needed about 2,000 years to cool down to 100° Celsius. After about 2 million years the 400 km2 lake silted up.
Today the large circular depression (diameter: 24 km) is still visible, known as the "Nördlinger Ries", with the beautiful middle-age town Nördlingen near the center.

* Photo by kind permission of © www.rieskrater-museum.de, Dr. Schieber.
* Photo by kind permission of © Landesmedienzentrum Baden-Württemberg and Albrecht Brugger.

Resources

Four tektite strewnfields are known worldwide. The moldavite resources belong to the central European strewnfield. Moldavites are mainly found in southern Bohemia and southern Moravia (both Czech Republic). Other resources are in the Waldviertel (Austria) and the Lausitz (eastern Germany). The relatively unimportant deposit south of Cheb (German: Eger) is alledgedly of alluvial origin.

The most famous deposits are in the first strewnfield near České Budějovice (German: Budweis): the sand pits near Ločenice and Vrábče, and the clay pit near Besednice. These moldavites are usually bottle-green and transparent.
Deposits in the second strewnfield near Brno (southern Moravia) contain darker, olive-green to brown moldavites.

Color and Quality

Fern-like Bohemian Moldavite *
Brown Moravian Moldavite *
Moldavites show different tints of green and brown: From light green to dark green, from olive to blueish green. Besides green ones also brownish moldavites can be found. Moldavites occur as discs, balls, drops, sticks and in other irregular shapes. In contrary to other tektites which show black, brown or grey colors, moldavites are the only green tektites.
The most sought-after moldavites for faceting are green in combination with a high transparency. The best of them show a special fern-like surface.



* Photo by kind permission of © http://skywalker.cochise.edu/wellerr/aawellerweb.htm, Roger Weller.
* Photo by kind permission of © http://www.moldavit.de, Th. Dehner.

Moravian Moldavites are usually much larger compared to Bohemian, but the color is usually on the brown side. Also they are much rarer compared to the Bohemian ones.
One can spend days walking the Moravian fields not finding a single one (average weight 11 g). On Bohemian fields one can find between 1 - 20+ a day (average weight 5 g).

Thanks to Ales Patrick Krivanek for his friendly support.

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