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Minerals/Fossils

Minerals/Fossils

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Datum izida:3/22/1999 11:00:00 PM
Oblikovanje:Matjaž Učakar
Motiv:Cinnabar and Blobs of Mercury
Tisk:DELO - TISKARNA d. d., Ljubljana
Izvedba:4-colour offset
Papir:Chancellor oba free L.S.PVA GMD 102g, gummed
Velikost:
Zobčanje:comb
Ilustracija:
Fotografija:Miran Udovč
Pošta:
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Minerals/Fossils

<b>Cinnabar and blobs of Mercury /Idrija</b><p>Cinnabar is mercuric sulfide (HgS) with 86.2 percent of mercury. Due to its crystal forms and symmetric elements it belongs to the trigonal trepezohedral type of symmetry. Most often it occurs in rhombohedral and acicular crystals. The name originates from Indiaand it means red pitch. It was already appreciated by antique painters. It can be identified by its bright to dark red &quot;cinnabar&quot; or also &quot;vermillion&quot; colour, a scarlet streak, high density (8.0 to 8.2 g/cm3) and perfect cleavage. It is often translucent, rarely transparent. Pure crystals have an adamantine to metallic luster while the fine-grained ones are opaque or dark when they contain additions of clay or organic substance.<br>Cinnabar crystals belong to the most important heritage of inanimate nature in Slovenia. In mineralogical collections around the world they are highly appreciated due to their rarity, bright colour and interesting combinations of crystal planes. Hardly any of them exceed the size of 1 cm. Most frequently they are only a few millimeters large.<br> Mercury (Hg) is a native element. The name hydrargyrum, meaning &quot;liquid silver&quot; in Latin, was given to it by Teophrast in 315 B.C. It is unique, as it is the only metal that is a free-flowing liquid at room temperature. It can be classified among minerals when it solidifies at –39 °C with crystallization forming trigonal - rhombohedral crystals. It can be identified by its silvery-white blobs with metallic luster and high density&#58; 13.6 g/cm3. Mercury is rare. It is often found in the form of cinnabar ore. Due to its vaporousness and toxicity, it is kept in collections in hermetically sealed transparent recipients.<br>Cinnabar and native mercury are the only sources of mercury. The latter is used in the electrical industry in rectifiers and in the industry producing measuring devices. In addition, it is used in the industry producing explosives, then as a catalyst in chemical industry, for the extraction of gold and silver from their ores and in amalgam used in dental fillings. Due to its toxicity, which was discovered rather late, its use in pharmacy and the production of pesticides is very limited.<br>Cinnabar is rarely found in quantities that might be interesting for industry. In the Idrijan ore deposit it occurs together with native mercury in the Carboniferous, Permian and lower and middle Triassic rocks. Cinnabar is more frequent in cracked Triassic limestone and dolomite. The ore deposit is about 1500 metres long and 300 to 600 metres wide. It extends 450 metres in depth. There were about 120 km of tunnels in use at 15 levels. The lowest was 30 metres below sea level.<br>Native mercury was discovered by accident in Idrija in 1490. In the mine's 500-year long history 12,757 million tons of ore was excavated, thereof 144,828 tons of mercury which represents 13 % of all world production so far, placing Idrija in the second place, right behind the Spanish town of Almaden. Due to the reduced use of mercury and fall in prices in the world market resulting from it, the process of gradual closing down began in 1988.<br>500-years of mining brought prosperity to the mining town of Idrija. Since 1575, at the time when the Austrian Habsburg monarchy became its owner, the mine was of special strategic and financial importance. The mine had the then state-of-the-art equipment and top-level personnel. Together with the mine and town, geology, mining and medicine of work were developed. Besides the mine, folk art – lacemaking developed as a supplementary activity. It enabled the development of cultural and educational activities, which was proved by the erection of the first theatre in Carniola in 1769 and the first Slovene grammar school in 1901.The town of Idrija, along with its surroundings, is a wonderful monument of natural, technical and cultural heritage that is well worth visiting.<p>Uroš Herlec, M.Sc., geologist<br>