Talc Enlarge
Aug.t 1. 1806. Publish’d by Ja.s Sowerby. London.
British Mineralogy
CLXXXIV
Silex Talcum

Talc

  • Div. 2. Imitative, in grains.

This forms an appearance not unlike Mortar with the green Chlorite among it. When it has a more perfect appearance of mortar without the green, it is considered as good manure, and is provincially called Gonlt. It is often found about a foot from the surface. This is chiefly used to make the best white bricks of Cambridgeshire. That with granular Talc or Chlorite is of a dull hue, and is found deeper. The same substance, somewhat more compact, is called in Ireland Mulatto-Stone: see tab. 185. I have figured some of the petrifactions that occur, considering them as useful to mineralogy. Those in this stone are generally of a dark brown stony appearance, accompanied by rugose lumps of various sizes of nearly the same substance, somewhat similar to the swampy Iron Ore of Kirwan, v. 2, 183. The petrifactions are coloured like it, sometimes with a nearer approach to the hue of Pyrites. These petrifactions are the round one on the left hand, supposed a hinder tooth of some fish; the right hand is considered as a fish’s bony palate; the middle upper figure is a bivalve shell, the upper valve remaining in the state of Carbonate of Lime, the lower one browned with the ore. It is a kind of Anomia called a Gryphite, very frequent among petrifactions. On the left, under that, is part of a Coral, near which is a fish’s palate, such as often extends to the form of a Lupin pod. The left hand figure below is part of a Cornu Ammonis. The rude lump of the brown ore on the right, with the adhering shells, like those of the Anomia Squamula, found sticking on crabs, oysters, &c., has the impression of the deeper valve of a small Gryphite.

In all our specimens of green sandy Talc, it has been so worn and rubbed about that it has lost its laminated texture, and become earthy in its fracture.

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