It is a brown to black metallic mineral which crystallizes in the tetragonal system.
2.
It crystallizes in the tetragonal system and occurs both in good crystals and as formless masses.
3.
"' Eskebornite "'is a tetragonal system and it has a brassy colour.
4.
Crookesite is an opaque, bluish grey to pink toned brown metallic mineral crystallizing in the tetragonal system.
5.
"' Berzelianite "'is a rare copper selenide mineral with the formula tetragonal system.
6.
A similar mineral, " sinjarite " the dihydrate of calcium chloride, crystallizes in the tetragonal system.
7.
The normal low-temperature form ?-spodumene is in the monoclinic system whereas the high-temperature ?-spodumene crystallizes in the tetragonal system.
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