Mining museum's treasures. Chalcedony
In Ancient Greece, extraction of gemstones was considered a matter of national importance. At times, the war could start at the territories if they were rich in precious stones. One such location was the city of Chalcedon, situated on the shore of the Sea of Marmara. Numerous stones of various colors and shades were mined there. Local people called them "chalcedony", which gave the name to the mineral itself.
Chalcedony is a microcryptocrystalline rock, one of the varieties of quartz, which consists of the finest fibers that can only be distinguished under a microscope. There is a huge amount of variations of this mineral – over a hundred of them, and each variety has its own name. For instance, green chalcedony is called chrysoprase, bright-red or orange varieties – carnelian, and bluish-gray is sapphirine. Some stones, such as agate, can be easily identified by concentric stripes; the others – as onyx, for example – by curved markings on the surface of the stone.
Since ancient times, this mineral has been used as an ornamental and jewelry material. Chalcedony deposits can be found everywhere the world. The biggest deposits are located in Brazil, Uruguay, India, USA and Canada. In Russia, chalcedony is mined in Siberia and in the Urals. In the collection of the Mining Museum, there are samples of chalcedony from the personal collection of Emperor Alexander I and mineralogist J. Forster. The samples date back to the beginning of the 19th century.
Chalcedony. The Faroe Islands, Denmark. From the collection of G.Forster, 1802
Chrysoprase. The Blue Vein deposit, Kazakhstan
Sarder. The Tuldun River, Transbaikalia
Quartzine. Spherulites. Ahalzihe, Georgia
Heliotrope, Grohau, Poland. A present of Emperor Alexander I, 1816