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Exotic Mineralogy

  • Syn. Lievrit. Werner.

I am happy in being enabled to present figures of perfectly crystallized Yenite, which I had to regret not having seen when I published the scopiform variety in tab. 29. I am indebted to the liberality of the Countess of Aylesford for the loan of the upper tender specimen; its matrix is acicular Epidote, accompanied by a little Quartz in minute crystals upon the surface: the lower specimen, showing two larger crystals upon the same matrix, was lent me by Mr. Heüland; they are both from Rio la Marine in the island of Elba. Half of one of the crystals of the lower specimen has been broken off for Haüy to examine, and the measures given by that able crystallographer in his Tableaux are as follow: the angles of the prism 112° 36′ and 67° 24′, and the incidence of the four triangular terminal faces upon it 128° 29′; the prism, however, is so much modified by triangular faces, that it approaches a rectangular one in appearance, or one of about 97° and 83°.

It is strongly suspected, even by Le Lievre, that what he called a scopiform variety, which I have figured at tab. 29. is a variety of Epidote mixed with more Iron than usual; and Bournon’s observation that it is transparent, and that the black appearance arises from the intensity of the green colour, favours this opinion; for the genuine crystals seem to be perfectly opaque and black. The specific gravity of a small piece of the scopiform variety in well defined square prisms, which I have examined, was only 3.000, while that of the crystals rises as high as 4.061: it is to be hoped, that when a greater supply is obtained this question will be clearly settled.

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