Sylvanite (Romania)
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A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 4900 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.
The telluride minerals contain one or more telluride anions (Te-2). The tellurides are usually considered together with the sulfide minerals, the arsenide minerals, and the sulfarsenide minerals.
Sylvanite is a rare precious metal telluride mineral, (Au,Ag)2Te4 - gold silver telluride. This mineral volatilizes at relatively low temperatures. With heating, the tellurium component of sylvanite readily vaporizes, leaving behind blebs of gold/silver.
Sylvanite has a metallic luster, a bright silver color, is fairly soft, and usually occurs in the form of elongated blades or small granular masses. It is known from only a few scattered localities on Earth and occurs with other telluride minerals such as calaverite (AuTe2 - gold telluride). Sylvanite is an important gold/silver ore mineral in precious metal telluride deposits such as the Golden Quadrilateral in Romania, near Kalgoorlie in western Australia, and the Cripple Creek Diatreme in Colorado, USA.
Photo gallery of sylvanite:
www.mindat.org/gallery.php?min=3849
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SylvanitSylvanit (kurz Sylvan), bergmännisch auch als Schrifterz bekannt, ist ein eher selten vorkommendes Mineral aus der Mineralklasse der „Sulfide und Sulfosalze“ mit der idealisierten chemischen Zusammensetzung AuAgTe4 und damit chemisch gesehen ein Gold-Silber-Tellurid, die chemisch mit den Sulfiden verwandt sind. .. weiterlesen