Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/43

Rh Jewell; in chlorite, and in brown and almost pulverulent mica in Huel Gorland. The crystals enclosed in the latter substance, it may be observed, are always of remarkable brilliancy and in well defined varieties. In the latter mine it also occurred with blue and green carbonate of copper; with fibrous arseniate of copper; in cubes with the green cubic arseniate of iron; with mispickel and pyrites. I possess one specimen from Cornwall, but from what mine is uncertain, in which it is accompanied by vitreous and yellow copper. It has been found in capillary crystals in Huel Gorland, Carharack and Tol Carn mines; in the latter in recomposed granite though but very sparingly. I have one specimen from Tin Croft mine, in which the red oxyd is intermingled with native copper, and with jasper of a line red colour.

There are perhaps but few minerals that exhibit so many beautiful and regular forms, although the modifications of its primitive crystal, hitherto noticed, are only six in number. Of these forms, four have been given by Haüy, which, with two or three delineated by Sowerby in his British Mineralogy, constitute the whole of what has been published relative to the crystallographical history of this interesting substance. My own attention has been particularly directed to this subject, by the possession of a large collection of specimens, chiefly from Huel Gorland mine; from which have been selected the principal varieties in the form of the crystal, which are here presented in a regular series. The number of these will doubtless be increased by future research. It does not seem requisite to offer detailed remarks on each individual crystal; it will suffice to make some occasional observations, and to note some peculiarities that might not be perfectly intelligible by the assistance of the figures alone.