Amorphous Carbonate of Lime
- Div. 3. Amorphous.
In tab. 79 I have figured the Red or Variegated Primitive Marble from Tirie; it is of a very fine grain: the present specimen is of an equally fine close waxy texture, semi-iransparent and white; it would be beautiful, if it could be got in massive blocks, for the purposes of the statuary. It however seems, from what I have of it, either to have brew gathered unskilfully, or it is generally of too slaty or fissile a structure for such purposes; and even when it looks uniform, it is often full of threads of Tremolite or granulæ of Quartz. It is heavier than common marble, and is said to have a portion of Carbonate of Magnesia in it; whence it has been ranked with the Dolomite, so named in honour of Dolomieu, who noticed such marble abroad; but which is not now considered a distinct species. The fine texture is its distinguishing character. I do not know any substance with which it may be compared in that respect, better than that of the Chama gigas, which has no appearance of granulæ or crystallization. The squarer piece in the back ground has less of the fissile divisions, and contains fewer of the hard granular that are so detrimental to it for the masons’ use. It has a small vein at the bottom partly crystallized. I believe it sometimes alternates with the other Tirie Marble, and sometimes with small grained Gneiss containing Garnets, &c.