.

Moldavite Mineral Facts:

Chemical Formula: Natural Glass - Meteoric
A natural glass consisting of roughly Silica, 77.75%; alumina, 12.90%; iron oxide, 2.60%; Calcium oxide, 3.05%; magnesium oxide, 0.22%; potasiu, oxide, 2.58%; sodium oxide, 0.26%; water, 0.10%. It is technically a rock rather than a mineral.

Colors: Medium dark green.
Much of the green color is imparted by iron in this glass.

Hardness: 5.5

Density: 2.32 to 2.36

Cleavage: A glass, not crystalline, so no cleavage observable.

Crystallography: Glass - no crystal structure

Luster:.  Vitreous luster. Normally transparent to translucent. 

Optics: (Refractive Index): = 1.51

Czech Republic Moldavite

Composition, Structure and Associated Minerals:
Moldavite is an olive-green or dull greenish natural glass substance that many believe was formed by the fusion of surface materials produced by a meteorite impact. It is considered to he a variety of tektite.

Identification and Diagnostics
A glass silicate of aluminum, calcium, potassium and iron. Unlike ordinary glass and obsidian it is almost infusible before the blowpipe, and when fused remains perfectly clear on cooling. It differs considerably in chemical composition from ordinary glass, having as it does a higher percentage of silica, considerable alumina, and a small percentage of alkalis. The percentages of silica range between 88 per cent and 78 per cent ; those of alumina between 5 per cent and 13 per cent ; and those of potash and soda between 1 per and 2.5 per cent. In ordinary glass the percentage of silica is not much above 50 per cent ; there is almost no alumina, while lime and magnesia amount to about 20 per cent, and potash and soda 20 per cent to 25 per cent.

Occurrence, Localities and Origins:
This term is applied to a transparent green stone found occurring
in small pieces in Bohemia, in the region drained by the river Moldau (also known as the Vltava), whence the name moldavite. There has long been a question as to the origin of this unique  material. The color of the stone is of the peculiar character generally designated as bottle-green; and since its physical characteristics, such as hardness, fracture, optical qualities, etc., also resemble those of glass, the view was long held that the fragments found were remains from some long since demolished and forgotten glass works. However there are no remains of any  glassworks in the neighborhood of its occurrence and pieces of the glass are widely distributed throughout Tertiary and early Pleistocene surface deposits in Bohemia and Moravia. At one time it was thought to be a form of obsidian, but the widespread occurrence of moldavite glass cannot be explained as the result of any volcanic agency as there are no nearby igneous sources that could have created it.

 Moldavite close up

Moldavite Selection

The most widely accepted opinion that the fragments originate from the fusion of surface soils and rock during the impact of a peculiar kind of meteorite. The material thus ejected from the impact site travels high into the atmosphere, even to the point of spending a short time in space before returning to the earth. These views are accepted for all tektites. The acceptance of this origin for moldavite has lent an added interest to it, and increased its use for jewelry and other applications. The pieces as found are water worn pebbles of various shapes, usually with deeply indented or pitted surfaces, as shown in the accompanying photos. In size they are never larger than one's fist, while they are usually much smaller. They are found in the beds of brooks and in the soil. Regions near Budweis and Trebitsch are especially prolific in the pebbles.  It is estimated that the moldavite glass was formed from an impact which happened about 15 million years ago.

Glassy tektite pebbles similar to moldavite are found on the island of Billiton, near Java. These are known as billitonite. They are also found in Borneo and several parts of Australia. In these places they are believed to be of the same type of meteoric impact origin. Of the four known different tektite occurrences, only the Bohemian moldavite glass is so far used to any extent in jewelry. Moldavite has been sold under the names of bottle-stone, or water - chrysolite. A natural glass of the same character has been found in water-worn fragments in Ceylon, and has been sold as peridot, which it resembles in color, but is readily distinguished from it by its very different physical properties. The total resource of Moldavite is estimated at 275 tons and there are now four moldavite mines that are in full operation in the Czech Republic. It is projected that inroughly ten years commercial Moldavite mining will come to an end. After this time, there will be virtually no appreciable amount of gem-grade Moldavite left in the ground. High-quality moldavite stones are often used in hand crafted jewelry and thus enters the market away from mainstream jewelry stores, more centered around art and craft style custom jewelry makers.

Return to the Mineral Collectors Information Page

Nevada Outback Gems