Lapis Calaminaris Ph. Lond. & Edinb. Cadmia fossilis; Cadmia lapidosa. Calamine or Calamy: a mineral substance, of a greyish, brownish, yellowish, or pale reddish colour, and sometimes of all these colours va-riously mixed; considerably heavy; and moderately hard, but never sufficiently so to strike fire with steel; when mixed with powdered charcoal, changing copper, by fusion, into a yellow metal, called brass. It is found plentifully in England, Germany, and other countries; either in distinct mines, or intermingled with the ores of lead or other metals.

The matter, which copper imbibes from this mineral in its conversion into brass, separates again from the brass on keeping it melted in an open vessel, and exhales in fumes; which con-dense, upon such adjacent bodies, as are less hot, into white flowers, the same with those into which zinc is converted by fire. A mixture of calamine and powdered charcoal yields by itself, in open vessels, or if the air is admitted, the same flowers: in close vessels, the zinc is revived, and either runs off, or sublimes, in its proper metallic form, into that part of the vessel which is most remote from the action of the fire. The quantity of zinc is variable, as of other metals in their ores: Marggraf informs us, in the Berlin memoirs, that some of the foreign calamines yielded two sixteenths of their weight, an English calamine three sixteenths, and another English specimen from Holywell in Flintshire, seven sixteenths: from several parcels of the common calamine of the shops, I have gained nine sixteenths. The most exact way of determining the quantity of zinc appears to be, by mixture with a pretty large proportion of copper; by which the zinc, resolved into fume, is imbibed and detained.

This ore of zinc, employed principally for the making of brass, is for that purpose roasted or calcined; partly with a view to dissipate some sulphuteous matter, which the crude mineral is supposed to contain; but chiefly to render it friable, and more easily reducible into fine powder. It is with the ore thus calcined, that the shops are generally supplied. The roasted calamine is levigated into an impalpable powder.

In this state it proves, for external purposes, an excellent restringent, desiccative, and epulo-tic; of great use in collyria, against defluxions of thin acrid humours upon the eyes; and in unguents and cerates, for cutaneous ulcerations and excoriations. The officinal epulotic cerate, commonly called Turner's, is made by melting six ounces of yellow wax in a pint of oil olive, over a gentle fire, sprinkling in six ounces of levigated calamine as soon as the mixture begins to grow stiff, and keeping the whole stirring till grown quite cold. The college of Edinburgh uses only one part of the calamine to five parts of a cerate composed of oil, wax, and spermaceti.