Cassiterite
Cassiterite ( tin ore, Nadelzinn ( ore ), Holzzinn, Visiergraupen, cassiterite ) is a commonly occurring mineral from the mineral class of " oxides and hydroxides ". It crystallizes in the tetragonal crystal system with the chemical composition of SnO2 and usually develops short to long prismatic, acicular or bipyramidal crystals, but also granular to massive aggregates in brown black, gray, yellow, brown, green or red. Even colorless crystals are known. Translucent crystals show weak dichroism in yellow and maroon.
- 5.1 as a raw material
- 5.2 as a gemstone
Etymology and history
The name derives from the Greek cassiterite κασσίτερος kassiteros for tin. From miners often resulting in short prismatic and knee- shaped winding crystal twins or a lot of nerds were called Visiergraupen. Aggregates in nieriger, glass head like design received the designation Holzzinn.
The mineral is due to its high tin content (hence cassiterite ) degraded BC since the 6th millennium and therefore one of the first ores that were used by people.
Classification
Oxygen = 1: In the old ( 8th edition ) and new classification of minerals ( 9th Edition ) by Strunz the cassiterite of the Department of the oxides with the molar ratio of metal 2 was assigned. In the new system, this department finds, however, a further subdivision, so that the mineral is now in the subsection "With medium-sized cations: chains of edge-sharing octahedra " can be found.
According to the classification of minerals according to Dana Cassiterite is one of the " simple oxides with quadruple positively charged cations ".
Education and Locations
Cassiterite occurs mainly in hydrothermal veins, greisen and granitic pegmatites. In addition, it is found as Seifenzinn in river sediments.
Historically significant were the deposits in the Erzgebirge, Fichtelgebirge and Cornwall. The most important deposits with today degradation are in Llallagua and Viloco in Bolivia, Hunan and Yunnan in the People's Republic of China, Indonesia, Malaysia and Peru.
Other localities are or were, among others, some regions in Afghanistan; the provinces of Constantine and Tamanrasset in Algeria; the provinces of Jujuy, Salta, San Juan and San Luis in Argentina; Rossarden / Tasmania and many other regions in Australia; Liège in Belgium; Belize; many regions in Bolivia; Amazonas, Bahia, Goiás and Minas Gerais in Brazil; many regions in the People's Republic of China; some regions of France; many regions in the United Kingdom; some regions in Canada; Katanga, Kivu and Maniema in the Democratic Republic of Congo; Hokkaido, Honshu and Kyushu in Japan; Madagascar; Mexico; Panasqueira in Portugal, Tenkergin / Chukchi Peninsula in the Russian Federation, Slavkov / Bohemia and Moravia in the Czech Republic; and many regions in the United States.
The cassiterite deposits in eastern Congo are in a conflict area, along with coltan, gold and cassiterite wolframite counts to the relevant conflict resources in this war.
Flow rates
The global output in 2008 stood at about 333,000 tonnes, while China accounted for 150,000 t, 100,000 t of Indonesia, Peru 38,000 t, 24,000 t Democratic Republic of Congo, Bolivia 16,000 t and 5,000 t Others.
Crystal structure
Cassiterite crystallizes in the tetragonal crystal system, space group P 4/mnm with the lattice parameters a = 4.738 Å, c = 3.118 Å and two formula units per unit cell.
Use
As a raw material
Cassiterite is the only world's major tin ore with a ( theoretical ) tin content of 78.8 percent. However, the tin atoms are replaced often, thus reducing the actual tin partially replaced by atoms of iron, titanium, niobium, tantalum or zirconium. Slags from Zinnverhüttung are therefore an important raw material for the extraction of tantalum.
Cassiterite is smelted at temperatures of about 1000 degrees Celsius. The tin obtained is used as a non-toxic, corrosion- resistant coating for steel tanks (tinplate ), and for the production of various household items such as plates or pots, but also ornamental and game items like tin soldiers. It is also used in alloys with lead as low melting solder.
As a gemstone
Well -formed crystals are processed into semi-precious stones. However, these are very sensitive to various acids and heating depending on the tin content. Cassiterite can be confused with colored diamonds, smoky quartz, scheelite, zircon and other color and luster due to easy.