. Bulletin - United States National Museum. Science. 402 BULLETIN 131, UNITED STATES NATIONAL MUSEUM with an index of refraction for lithium light of ±.02 and for sodium light, ±.02. It seems probable that it is an isometric paramorph after either a tetragonal or an orthorhombic form as many of the complex pegmatite uranium minerals seem to be. Also like nearly all of the complex pegmatite minerals this mineral is variable in composition and the specific gravity of the specimens tested ranges from to as determined with the Joly bal- ance. The specimens analyzed had a specific
. Bulletin - United States National Museum. Science. 402 BULLETIN 131, UNITED STATES NATIONAL MUSEUM with an index of refraction for lithium light of ±.02 and for sodium light, ±.02. It seems probable that it is an isometric paramorph after either a tetragonal or an orthorhombic form as many of the complex pegmatite uranium minerals seem to be. Also like nearly all of the complex pegmatite minerals this mineral is variable in composition and the specific gravity of the specimens tested ranges from to as determined with the Joly bal- ance. The specimens analyzed had a specific gravity of (by pycnometer). The radioactivity of specimens of different specific gravities showed slight differences as tested by the exposure of a photographic plate, those having the highest specific gravity appearing most active (pi. 14). The material was not tested with an electroscope. Pieces of like content of uranium and thorium were selected on the basis of comparative radioactivity. Two of the least active pieces from the seventh row (pi. 14) gave on analysis 35 per cent Ti02 compared with 39 per cent in the best material. If available in quantity this mineral would be of value as a source of radium, but probably only a few pounds could be secured even at prohibitive cost. The analysis of such a complex mineral is so difficult that too much weight can not be attached to the percentage figures. The mineral is slowly decomposed by treatment with concentrated sulphuric acid or by hydrofluoric and sulphuric acids. It is more convenient, however, to bring it into solution by gentle fusion with acid sodium sulphate. On dissolving the melt in cold water or dilute sulphuric acid there remains a small residue consisting of silica, unattacked mineral, and sulphates of lead, barium, and strontium. The analysis gave the following results: Analysis of brannerite from Stanley Basin, Idaho [R. C. Wells, analyst] Silica (SiOs) Titanium dioxide (TiOj). Ferrous oxide (FeO) Lime(
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