Note upon the occurrence of Sphene in the Granite of the Sierra Nevada.
BY WILLIAM P. BLAKE.
Sphene, in small hair-brown or amber-colored crystals, appears to be abundantly distributed in the granite of the Sierra Nevada. It may be found at the sources of the American River, in the exposures of granite about Slippery Ford, and other points, and upon the Mokelumne River, further south. The crystals are seldom more than the thirty second part of an inch in diameter, and are not conspicuous, but may be found in almost any specimen of the rocks.
It appears, that this mineral is also of common occurrence in the granite of the British Islands. In a report to the British Association, (1863) upon the composition of the granite of Donegal, it is stated, that the rock contains, almost universally, small crystals of sphene, in some varieties so abundantly, as to induce the authors of the Report to term it “sphene granite.” It is also observed that this mineral has long been known to exist in the granite of parts of Scotland, and in that of Galway.