Oxide of Uranium, Uran-glimmer

These curious varieties of tins rare substance are so remarkable, and have so different an appearance, that they may naturally be mistaken, without particular attention. The crystals are, however, mostly square plates, but heaped or grouped in little fasciculi, which give them a more cubical appearance than usual. Some are placed so as to give a fan-like form, being a little elongated, and placed nearer each other at the base of attachment. They vary also in some other respects, but particularly the arrangement of the minute crystals in a linear order. This specimen was brought from Cornwall by Mr. Mawe.

The specimen figured below was presented to me by Mr. Fox; it is in much larger plates than usual, and extremely thin: their rectangular figure is, however, distinctly marked on the plates, which stand in broad fasciculi in different directions: they are very tender, fracturing easily into very thin sparkling Glimmer. The gangue is Red and Black Quartz, or lied Jasperine Quartz. The specimens are from Tolcairn mine.