Penouta mines, Viana do Bolo, Orense (Ourense), Galicia, Spain

SnO₂

Crystal System: tetragonal
Colour: black, yellow, brown, red or white
Lustre: adamantine, greasy, sub-metallic
Habitus: prismatic
Fracture: irregular/uneven or sub-conchoidal
Cleavage: imperfect/fair {100} imperfect, {110} indistinct.
Hardness: 6 - 7
Density: 6.993 g/cm³ 
Origin and geological occurrence: cassiterite occurs in high-temperature hydrothermal veins and in pegmatites related to granite intrusions. It may also be found in alluvial placers, sometimes in economically valuable deposits (e.g., in Malaysia).

www.mindat.org
Smorf link

Samples:

	4.1 Cassiterite Compact black masses of cassiterite with quartz. #oxides
	4.26 Cassiterite Equant brownish crystals of cassiterite. #economic minerals