Carbonate of Lime

This shows specimens with the facets common to both the preceding ones, and their relations to both; to the former, from retaining the original six flat tables and the bevilling with sharper angles, while those of the latter are rounding into the whole form. In speaking of these, it would seem convenient for instruction to suppose the molecules about to place themselves in due order, but interrupted by something like a thickness in the fluid, yet to be accounted for, and which leaves a desideratum to be filled up by physical and chemical investigation. The form of the Pearl-spar, tab. 19, might seem to me to be the mechanical effect of Iron in the solvent; yet we find those that are apparently without Iron forming those curving modifications:—may it be when they are more suddenly left by the solvent that they become sharpest, and vice versa? for we find that Magnesian Crystals are often sharp, although frequently somewhat less so than the common Carbonate of Lime.

It is somewhat remarkable, that this Carbonate of Lime is on a brownish crystallized Pearlspar that seems Magnesian, similar in substance to tab. 217.