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The Mineral Cassiterite

bornite picture

bornite picture

bornite picture

Cassiterite is tin oxide and generally opaque, though its thin crystals are translucent. Because of its sheen and multi-faceted crystals (multiple crystal faces). It is an attractive gem. As its crystals have many faces, it looks sparkling. Since ages, it has been the main  ore of tin and continues to be so even today.

Chemical Formula  
SnO2

Derivation of Name  
Its name derives  from the Greek word “kassiteros,” meaning "tin,”  or from the Phoenician “Cassiterid”, a pointer to the islands of Britain and Ireland, the earliest known sources of tin.

Occurrence      

Small quantities of the Cassiterite mineral  are frequently found in igneous rocks. Deposits in Bolivia and old mines of Cornwall in England have had the highest concentration of quartz and pegmatite along with granitic intrusive. Generally, the deposits have Tourmaline, Topaz, Arsenopyrite, Apatite, Fluorite, Molybdenite and Wolframite. The mineral widely appears as surface deposits.

Gemology
The clarity of Cassiterite material varies from transparent to opaque. Besides, there exists a minor property of translucency in this thin crystal. In Cassiterite, there is a  very striking faultily metallic impenetrable luster. Basically, this is a collector’s stone and frequently it is formed into facets for exhibiting purposes. The majority of the stones do not possess good shapes, but they are given a good finish by polishing. The banded cassiterite, otherwise known as wood tin is frequently given a cabochon cut as jewelry

Source 
You can find cassiterite today in placer  or alluvial  deposits that contain the resistant weather-beaten grains. The hydrothermal veins in the tin mines in Bolivia offer the best primary cassiterite source.  Rwanda also is developing  a new industry for cassiterite mining. In the Democratic Republic of Congo  the competition for this mineral has increased fighting in Eastern Congo, leading many to give it the status of a conflict mineral.

Mineralogy  
Cassiterite is the most popular mineral of tin. Since ages it has been used as the principal ore of tin and even today it fulfills the same requirement. Many of its deposits can be found in placer stream deposits wherein this heavy mineral gets collected in the form of rounded water-worn nuggets. Quite often,  you can find it next to other minerals like  Tourmaline, Topaz, Fluorite, and Apatite.

Color           
It occurs in brown, reddish-brown, black, reddish-black or yellowish-brown colors. Rarely is it found in gray or yellow colors. The Wood Tin variety has inner concentric, ringlike band growths.       

Density                              
6.993 g/cm3

Mohs scale hardness
6–7

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