Dodecaëdral crystallized Carbonate of Lime

Some Carbonates of Lime, with regard to their crystallization, are not uncommon. This however is of the scarce kind; and was it not for the manner in which the modification appears to be formed, it might, under the common idea of its being a rhomboidal dodecaëdron, might be esteemed as a Garnet, or some other substance that commonly exhibits that figure.—The fracture of Carbonate of Lime is very apparent in it; as well as the shapes of the primitive rhombs, which will be found to agree with the figure of the fracture; and are placed in such a manner as to form the dodecaëdron. Thus we find the column is formed of laminæ placed on the face of the rhomb decreasing from the lateral edges. Its termination is at one or both ends, clearly in the form of the equiaxe.—The middle figure expresses this with the fracture, which is mostly on the edges. The whole is a sort of inverse crystal; the column being, as it were, formed contrary to the usual custom.

The specimen from which this figure was taken was lent us by our friend Mr. Rich. Phillips, who brought it from the North.