Moldavite – The Gemstone That Fell To The Earth
The origin of Czech moldavites, also known as the Vltavines, is most likely connected with an event that happened about 14.7 million years ago. At that time a huge meteorite around 1 km in diameter hit the borderland between what is today southern Bavaria and Baden-Württemberg. The impact left traces that are still visible today, namely the 24-km wide Ries crater, in which the city of Nördlingen was built, and the Vltavines. The energy released by the impact of this large body instantly melted the surrounding rocks and glassy masses were ejected to heights of up to 200 km and distances as far as 450 km. Fragments of this semi-liquid mass that had been transformed into aerodynamic shapes on their way through the atmosphere (drops, spheres, rotating discs, doubled drops - dumbbells, etc.) fell down on a Tertiary plateau with large lakes. This territory is today called South Bohemia. South Bohemia is the most famous moldavite site today, but there are also other sites in the Czech Republic where these gemstones can be found. One of them is near Dukovany and Třebíč in South Moravia. Other recently discovered sites include the moldavite fields in the Cheb Basin or sediments in the vicinity of Dresden. Rare occurrence of Vltavines has been documented, although with less reliability, in Upper Austria in the borderland at the south-eastern end of the Třeboň Basin. Rare finds of Vltavines are reported from the Elbe River Basin or the Vltava Terraces near Prague.
The Vltavines belong genetically to natural glasses, or more specifically, to tektites (from the Greek word tektos = molten). The tektites also can be found in other regions worldwide (the Philippines, Thailand, Vietnam, Java, Indochina and Russia). However, as a rule only the Vltavines are green, and save for minor exceptions, they are translucent. These physical properties justifiable rank them among unique items in the world. Their hardness is between 6.4 and 6.7 on the Mohs scale of mineral hardness.
The name Vltavine (sometimes also moldavite) was introduced in 1836 by F. X. M. Zippe, the custodian of mineral collections at the National Museum in Prague, who named the gemstones after Týn nad Vltavou (Moldatutein) as the first official discovery field. A typical feature of these gemstones is their deeply pitted surface, also called sculptation. The relief of the Vltavines depends on the chemical corrosion and permeability of the environment in which the Vltavines had been deposited. The surface of the Vltavines is etched by acids that are formed due to slow chemical processes as a result of the decay of minerals, which the sediment is composed of. The gemstone can be deeply pitted as is typically the case of Vltavines coming from the sites of Besednice, Dobrkovská Lhotka or Nesměň. The surface with fine-scale sculpting can be found very often on the Vltavines from the sites of Chlum nad Malší, Krasejovka, Slavče, Chrášťany, and many others. The pitted surface is characteristic for the Vltavines from the surroundings of Vrábče, Koroseky or Něchov. Nevertheless, we can say that except for the specific type of sculptation that is typical (save for rare exceptions) solely for the Besednice site, all the above-mentioned types of sculptation can be found on each of the sites. Similarly, the lustre of the Vltavines varies strongly from high-glossy through varnish-like to the fully matte appearance that is typical for the Vltavines from the sites of Jankov or Brusná. The green colour that distinguishes the Vltavines from the other tektites carries a full range of shades, from poison emerald to grass green or brownish green (Jakule site). There are also extremely rare dark brown Muong - Nong moldavites. True rarities are light green Vltavines known from the surroundings of Radomilice and Vodňany. The Vltavines discovered on farmland topsoil are often damaged by agricultural machinery and their surface is usually worn due to their permanent motion in the topsoil.
Vltavines are mainly found in clayey, clayey-sandy or gravelly and sandy sediments of the Tertiary period. The features of the sediments in which they are deposited depend mainly on the geological environment in which they have been transported and deposited. Although ten scientific conferences were held in the past to deal with the issues of the Vltavines and their origin, the process by which various types of Vltavines were deposited in the sediments has never been fully proven and documented. The types of Vltavine deposits in the sediments can be roughly divided as follows:
It is difficult to accurately reconstruct the process in which the Vltavines were deposited based on the relics of the sediments that have been preserved to the present day. Vltavines are often turned up when ploughing the fields. After washing out in the rain they can be easily discovered. Topsoil containing Vltavines often has a different colour than the surrounding areas. This is attributed to the presence of Vltavine-bearing gravels, sands or clays. Other sites where Vltavines can be found are sand or gravel quarries. Vltavines can be found in the moldavite-bearing layers immediately in-situ there. However, it is extremely dangerous to collect Vltavines in this way. Serious injuries with tragic consequences have occurred as a result of illegal digging.
The Vltavines belong genetically to natural glasses, or more specifically, to tektites (from the Greek word tektos = molten). The tektites also can be found in other regions worldwide (the Philippines, Thailand, Vietnam, Java, Indochina and Russia). However, as a rule only the Vltavines are green, and save for minor exceptions, they are translucent. These physical properties justifiable rank them among unique items in the world. Their hardness is between 6.4 and 6.7 on the Mohs scale of mineral hardness.
The name Vltavine (sometimes also moldavite) was introduced in 1836 by F. X. M. Zippe, the custodian of mineral collections at the National Museum in Prague, who named the gemstones after Týn nad Vltavou (Moldatutein) as the first official discovery field. A typical feature of these gemstones is their deeply pitted surface, also called sculptation. The relief of the Vltavines depends on the chemical corrosion and permeability of the environment in which the Vltavines had been deposited. The surface of the Vltavines is etched by acids that are formed due to slow chemical processes as a result of the decay of minerals, which the sediment is composed of. The gemstone can be deeply pitted as is typically the case of Vltavines coming from the sites of Besednice, Dobrkovská Lhotka or Nesměň. The surface with fine-scale sculpting can be found very often on the Vltavines from the sites of Chlum nad Malší, Krasejovka, Slavče, Chrášťany, and many others. The pitted surface is characteristic for the Vltavines from the surroundings of Vrábče, Koroseky or Něchov. Nevertheless, we can say that except for the specific type of sculptation that is typical (save for rare exceptions) solely for the Besednice site, all the above-mentioned types of sculptation can be found on each of the sites. Similarly, the lustre of the Vltavines varies strongly from high-glossy through varnish-like to the fully matte appearance that is typical for the Vltavines from the sites of Jankov or Brusná. The green colour that distinguishes the Vltavines from the other tektites carries a full range of shades, from poison emerald to grass green or brownish green (Jakule site). There are also extremely rare dark brown Muong - Nong moldavites. True rarities are light green Vltavines known from the surroundings of Radomilice and Vodňany. The Vltavines discovered on farmland topsoil are often damaged by agricultural machinery and their surface is usually worn due to their permanent motion in the topsoil.
Vltavines are mainly found in clayey, clayey-sandy or gravelly and sandy sediments of the Tertiary period. The features of the sediments in which they are deposited depend mainly on the geological environment in which they have been transported and deposited. Although ten scientific conferences were held in the past to deal with the issues of the Vltavines and their origin, the process by which various types of Vltavines were deposited in the sediments has never been fully proven and documented. The types of Vltavine deposits in the sediments can be roughly divided as follows:
- Miocene sediments (Vrábče strata). Vltavines were deposited in these sediments shortly after their impact from a very short distance into depressions in the ground. Typical sites are Jankov, Brusná, Vrábče - Nová hospoda, Slavče - Adámek, Slavče near Trhové Sviny, Habří, Lipí, Kvítkovice, Chrášťany and Besednice. These locations are characterized by high concentrations of Vltavines in the sediments.
- Pliocene sediments (Koroseky gravel sands). These are fluvial sediments and the Vltavines that are present there have undergone long transport. Therefore, they usually feature less textured sculptation. Where deposited in the chemically corrosive environment of the original sediments, they feature a very distinct weathering pattern. Locations: Vrábče, Koroseky, Kosov, Milíkovice, Chlum nad Malší, Něchov, Nesměň.
- Neogene alluvial fans. The Vltavines are usually deposited in gravelly and sandy sediments that are often very coarse. They usually feature a deeply pitted surface. Locations: Třebanice, Třešňový Újezdec, Lhenice.
- Quaternary sediments. They include mainly hillside loams or terrace sediments or beds of present-day water courses. If the sediments are mixed with original Tertiary deposits, the Vltavines may even have a well-preserved or rubbed down but newly gained lustrous sculptation that can be very fine. Nevertheless, the stones are often worn and damaged.
It is difficult to accurately reconstruct the process in which the Vltavines were deposited based on the relics of the sediments that have been preserved to the present day. Vltavines are often turned up when ploughing the fields. After washing out in the rain they can be easily discovered. Topsoil containing Vltavines often has a different colour than the surrounding areas. This is attributed to the presence of Vltavine-bearing gravels, sands or clays. Other sites where Vltavines can be found are sand or gravel quarries. Vltavines can be found in the moldavite-bearing layers immediately in-situ there. However, it is extremely dangerous to collect Vltavines in this way. Serious injuries with tragic consequences have occurred as a result of illegal digging.