Calcite and Malachite

White Calcite on Malachite. Calcite (CaCO3) can be white, colourless, pale shades of grey, yellow, red, green, blue or brown to 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 rhombohedrons, scalenohedrons or prisms but can also be tabular, acicular, cleavable, granular, compact, stalactitic, oolitic or earthy. Twinned crystals are common. Malachite (Cu2CO3(OH)2) can be emerald-green, grass-green or dark green in colour. Lustre is adamantine, silky or dull ands streak is light green. Hardness is 3 1/2 to 4 and cleavage is perfect in one direction crosswise. Malachite can be short or long prismatic crystals (rare) but usually occurs as radial, fibrous, botryoidal, stalactitic, incrusting or earthy.