II. On the Oxyd of Uranium, the production of Cornwall, together with a description and series of its Crystalline forms.
By William Phillips, Member of the Geological Society.
The only mine in Cornwall which until within the last few
years was known to have yielded the oxyd of uranium, was that
called Carharack, which was situated about two miles nearly south
of St. Die. The crystals on a specimen from that mine in my
possession are tabular, of a green colour and transparent, except
such of them as are partially or wholly coated by a deposition of
an ochreous substance, similar to that termed gossan by the miner.
This substance also is interposed between an aggregated quartz
tinged with iron, and the crystals; some of which are imbedded in
it. It may therefore be termed, in regard to this specimen, the
matrix of the crystals. On many of them have been deposited
numerous minute cubes of a light green colour; which, as there is
a considerable deposition of cubic arseniated iron in a cavity of
the same specimen, I consider to be that substance rather than the
oxyd of uranium: for though the latter sometimes takes a form so
nearly approaching to the cube as that the eye cannot perceive any
difference, yet such instances are certainly not very common.
In 1805, I noticed some crystals of the oxyd of uranium on the refuse heaps of Tin Croft mine, which is at the foot of a granitic hill called Carnbrae near Redruth; the veins of that mine run
