a mineral consisting of hydrated aluminium phosphate, A 1 3 (OH) 3 (P O 4) 2 411-120, crystallizing in the ortho - rhombic system. Distinct crystals are of rare occurrence, the mineral usually taking the form of hemispherical or globular aggregates with an internal radiated structure. It is translucent and varies in colour from grey or white to greenish, yellowish, &c. The hardness is 31, and the specific gravity 2.32. It was first found, at the end of the 18th century, by Dr W. Wavell near Barnstaple in Devonshire, where it lines crevices in a black slaty rock. It has also been found in Ireland (Tipperary and Cork), Arkansas, &c. (L. J. S.)