Fluate of Lime, or Fluor

These specimens are among the rarest of the fluors known in Great Britain. The upper one is in the possession of my very generous friend Philip Rashleigh, Esq. F.R.S. &c. of Menabilly in Cornwall, whose work and grand collection of British minerals are well known. It is an instructive specimen, having the form of a purple octaëdral nucleus withinside, and the green modification in order about it, which adds to the beauty as well as curiosity. One side of this octaëdron has many small but perfect cubico-octaëdrons (or cubes with the corners truncated) of pyrites. the next specimen in value I have the pleasure to possess myself. It is somewhat rougher and rather duller, standing on a confused octaëdron, the corners of which are rather prominent, forming, as it were, irregular steps, it includes a small octaëdron greener than the rest, but rather obscure, within which is a smaller purple one, but which is not to be seen without turning the specimen about many ways. They both come from the St. Agnes in Cornwall.

The lower geometrical figure explains this modifiction complete, in a position to make it familiar, and to show the placing of the octaëdron, which is in the position of the common fractures of all fluates of lime. See Tab. 27. and and the latter part of the corresponding description. The upper middle four-sided face in all the figures will be found to agree with the face of the cube common to fluate of lime; the four sides of which are bevelled off, and the corners, as before mentioned, are parallel to the faces of the octaëdron, they forming six square faces of the cube, eight faces of the octaëdron, and 24 bevellings; in all 38 faces.