Diaspore is an aluminium oxide hydroxide mineral (AlO(OH)), one of the constituent minerals of the aluminium ore bauxite. It is translucent or transparent, and usually colourless, white, yellowish, or brown in colour but may occasionally be lilac or pink coloured. It has a hardness of 6.5-7, a white streak, and a specific gravity of 3.2-3.5. Crystals are usually flattened, but this mineral more commonly occurs as lamellar or scaly masses. It has a perfect cleavage, with a pearly lustre on the cleavage faces. Diaspore decrepitates (crackles and breaks up when heated) and releases water. This behaviour is actually what is alluded to in the mineral’s name, which comes from the Greek word meaning “to scatter”. Zultanite is a trade name for pleochroic gem quality diaspore from southwest Turkey.
Image 1: Diaspore from Wessels Mine, South Africa. An unusual colour for this mineral, owing to manganese replacing some of the aluminum. From irocks.com
Image 2: Plates of pearly diaspore on matrix from Chester Emery Mines, Massachusetts, USA. From irocks.com