- Class 2. Earths.
- Ord. 1. Homogeneous.
- Gen. 1. Argilla.
- Spec. . Pinite.
- Pinit. Haüy Tabl. 53. Bournon, Catal. 123.
- Micarelle. Kirwan.
St. Michael’s Mount produced the present specimen. I am highly pleased to be able to give it as British, and to acknowledge the opportunity of doing so, as one of the many favours conferred upon me by the Count de Bournon. The finer specimens of Pinite are usually brought from a mine called Pini, at Schneeberg in Saxony: in them the Pinite is usually imbedded in Granite; but both the Count and myself have found large specimens containing square prisms, in masses of a kind of decomposing Porphyry, brought as ballast, to mend the roads; but from whence, we have not been able to ascertain with certainty: these masses are also remarkable for large hexaëdral prisms of dark reddish brown Mica, which have numerous vesicles in them as if they had been subjected to the action of volcanic fire. The Finite is still solid, but brittle.
The upper specimen is a somewhat decomposed granular Feldspar, in which are small octaëdral columns. The other figures are taken from foreign specimens for the sake of illustration; one of them is from Auvergne.
The texture of Pinite approaches to that of Steatite, but it is not quite so soft: its lamellar fracture, from which it takes the name Micurelle, is very indistinct, except near the ends of the crystals from Pini, to which it gives a metallic lustre. It is infusible before the blowpipe. Its primitive form, according to Haüy, is an hexaëdral prism; and he considers the square prisms which sometimes occur, as produced by a great enlargement of two primitive and two secondary faces of the dodecaëdral prism; but the Count de Bournou informs me that the rectangular prism is the primitive form: and this opinion is certainly well supported by his excellent series of crystals. The outline explains both these opinions. Spec. Grav. 2.980.
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