This, when genuine, is an ore of zinc consisting chiefly of the carbonate of that metal. It is in hard masses, which are first heated, then pulverized, and afterwards submitted to the processes of levigation and elutriation, in order to reduce them to the state of fine impalpable powder, in which state it constitutes prepared calamine.

Both the crude calamine and the prepared, though formerly recognized in our own and all the British Pharmacopoeias, have been entirely discarded, in consequence of uncertainty as to its genuineness; substances having been substituted for it, which often do not contain a particle of zinc.

Prepared Calamine (Calamina Praeparata, U. S. 1850) is in the form of a powder of various colours, according to the particular specimen of ore from which it may have been obtained, either pinkish, yellowish or brownish. It is inodorous and tasteless, and quite insoluble in water. Sometimes it is in small pulverulent lumps. The sophisticated article often found in the shops is generally of a pink colour. Calamine has the same properties, and is used for the same purposes, and in the same manner as the precipitated carbonate. There was formerly an officinal cerate called Calamine Cerate (Ceratum Calaminae, U. S. 1850), or Turner's cerate, which was made by mixing prepared calamine with yellow wax and lard melted together. It has been superseded by the cerate of carbonate of zinc, mentioned above.