Calcite and Fluorite

Calcite (CaCO3) can be white, colourless, pale shades of grey, yellow, red, green, blue or can be brown and black when impure. Lustre is vitreous or dull and streak is white. Hardness is 3 and cleavage is perfect in three directions forming a rhombohedron. Calcite usually occurs as rhombohedron, scalenohedron, prisms, tabular, acicular, cleavable, granular, compact, stalactitic, oolitic or earthy. Twinned crystals are also quite common. Fluorite (CaF2) ranges in colour from violet to white with a vitreous lustre and a white streak. Hardness is 4 and cleavage is perfect in four directions forming an octahedron. Fluorite usually occurs as cubic or penetration twins but can also be dodecahedral, cleavage masses, granular or columnar.