DIASPORE, a native aluminium hydroxide, A10 (OH) or crystallizing in the orthorhombic system and isomor phous with goethite and manganite. It occurs sometimes as platy crystals, but usually as lamellar or scaly masses, the flattened sur face being a direction of perfect cleavage on which the lustre is markedly pearly in character. It is colourless or greyish-white, yellowish, sometimes violet in colour, and varies from translucent to transparent. It may be readily distinguished from other colour less transparent minerals, with a perfect cleavage and pearly lustre—mica, talc, brucite, gypsum—by its greater hardness of 62 7. The specific gravity is 3.4. When heated before the blow pipe it decrepitates violently, breaking up into white scales.