Crystallized Carbonate of Lime

This curious specimen is from Wanlockhead in Scotland. Besides the whole group being formed like a cone, the individuals are a curious crystallization with a three-sided column somewhat rounding and truncated at the apex, and a central depression. The sides of the column are again divided into four facets, better understood by the figure than by description. The apex is formed of a six-sided facet.

We thought it somewhat resembled the hard Carbonate of Lime; but the fracture and its softness give evident proofs of the contrary. We do not know that this modification is to be found in any cabinet but in that of Mr. Laing, which contains the specimen here figured. It is formed as it were from the edges of the nucleus or primitive rhomb, with the obtuse angle upwards; the laminæ decrease less than in the metastatic, and consequently form a longer pyramid, which, as it is inclined to be rounding, cannot be measured. The truncations nearly on the column and those on the pyramid give it an odd appearance, more especially that on the apex, which has a rising margin. The order of formation from regular nuclei shows how much variety nature is capable of producing by the most simple means.

The specimen is a little coloured towards the bottom with ochraceous Oxide of Iron, and in some parts are a few blotches of decomposing Pyrites.