One of the least known precious stones. It was first defined by the
American mineralogist,
Davis, after it was found in
Cedar Valley near
Lake Utah,
USA, so far the only place it has been found. It appears in small quantities in association with variscite utahlite, on whose nodules it forms oolite in compact layers. As a precious stone it comes into consideration only when together with variscite. It developed in this deposit in underground layers from the effects of the gradually infiltrating ground waters containing dissolved phosphates, and from their influence on rocks rich in aluminium.
A number of various phosphates and other minerals develop with it. Apart from variscite, these are chiefly wavellite, millisite, gordonite, crandallite, the internally crystalline apatite, chalcedony, goethite and clinvariscite. The above mentioned millisite is a hydrous basic phosphate of aluminium, calcium and sodium, which orms grey fibrous concretions. Gordonite, triclinic hydous basic aluminium-magnesium phosphate, usually occurs in colourless layers, and only rarely in crystallized form. The earthy-yellow crandallite is a hydrous basic aluminium-calcium phosphate. Clinovariscite (or metavariscite) resembles variscite in appearance and composition, but is monoclinic. The 'eye-like' forms of these phosphates, formed by concentric layers, are particularly popular. Such specimins are polished as ornamental stones.