Morganite

morganite, gem-quality beryl (q.v.) coloured pink or rose-lilac by the presence of cesium. It is often found with peach, orange, or pinkish yellow beryl (also called morganite); these colours transform to pink or purplish upon high-temperature heat treatment. Morganite crystals often show colour banding: blue near the base, through nearly colourless in the centre, to peach or pink at the terminations. This colour change is probably caused by differences in the composition of the solution from which the crystal grew. Morganite is commonly found as squat, tabular crystals in lithia pegmatites, as in southern California and New England.