The following analyses are of serpentines derived from a peridotitepyroxenite dike: H. Almost black. Possibly derived from adjacent shale. I. Almost black. Derived from pyroxenite. J. Bastite. Derived from pyroxenite. Record No. 1166. Accidental organic matter was deducted from analyses H and I, with subsequent recalculation of the data to 100 per cent. L. Serpentine. M. Talc-like, yellowish-green serpentine. N. Weathered serpentine. O. Olive colored, probably serpentine. Samples H, I, and J are from near Bagley Creek; K, L, M, and N from near Arroyo del Cerro; O from Ferguson ravine. M and O carry considerable chromite. 15. MISCELLANEOUS ROCKS. A. Rhyolitic obsidian, Medicine Lake, Modoc County. Collected by J. S. Diller, who reports it to be a banded obsidian, containing a few minute feldspar crystals. The banding is due to a multitude of trichites. Analysis by L. G. Eakins, record No. 1072. B. Tuff from Hyampom, south fork of Trinity River, Trinity County. Almost wholly made up of particles of clear glass. Collected and described by Diller. Analysis by George Steiger, record No. 1427. C. Diabase-porphyrite, one-half mile west of Browns Valley, Yuba County. Collected and described by W. Lindgren. Contains augite, plagioclase, magnetite, chlorite, and epidote. Analysis by W. F. Hillebrand, record No. 1419. D. Amphibolitic schist, 1 mile northeast of Browns Valley, Yuba County. Collected and described by W. Lindgren. From metamorphosis of C. Contains chiefly green hornblende and feldspar. Analysis by Hillebrand, No. 1419. E. Basalt, base of a lava flow, east of the head of the San Joaquin River, Madera County. Description supplied by Turner. Hitherto unpublished. Contains pyroxene, partly augite, plagioclase, olivine, and iron ores. Analysis by W. F. Hillebrand, record No. 1767. F. Olivine-basalt, west peak of the Dardanelles, Alpine County. Described by Ransome in Bull. 89. Contains olivine, largely altered to iddingsite, plagioclase, serpentine, and augite. Analysis by George Steiger, record No. 1697. G. Mica separated from quartz-monzonite, near Bloods Station, Alpine County. Described by Turner in Amer. Journ. Sci., 4th series, vol. 7, p. 294. Analysis by William Valentine, record No. 1736. H. Scoriaceous rhyolite, Mono Craters, south of Mono Lake. Described by Russell in 8th Ann., Part I, p. 380. Analysis by T. M. Chatard, record No. 36. I. Obsidian, Mono Lake. Analysis by W. H. Melville, record No. 1346. Described by Lindgren in Bull. 150, p. 149. P. R. C. 60. J. Pumice, Mono Lake. Analysis by Melville, No. 1346. Described by Lindgren in Bull. 150, p. 148. P. R. C. 59. K. Volcanic ash, east shore of Owens Lake. Collected and analyzed by Chatard, record No. 783. |
