Carbonate of Lime

A rare modification of Carbonate of Lime from Derbyshire, The faces of the column being alternately broader and narrower at the ends would, if extended, make an acute rhomb, formed by a slight deviation from the law by which the regular hexhaedral prism is produced. The apex is formed by three faces corresponding with those of the equiaxed rhomb, tab. 13 and 128, rendered pentagonal, and contracted as it were into narrow facets, by the broader ends of the columnar faces which approach the axis in the direction of the edges of the rhomb; whence Haüy’s name. It is generally found more or less covered with a brown crust, and has a roughish aspect given it by a mixture of earthy Oxide of Iron.

The lower figure is less acute, and has also the equiaxed termination: this also is rare, and is coloured a little. Both are upon tabular Sulphate of Barytes.