166 ANALYSES OF ROCKS AND MINERALS, 1880—1908. 
KicO wcccetacaewmcbd nines 
HO athe soi cccccsenc 
ue above 105° 
100.13 | 100.04 
OREGON. 
1. BASALT, MOUNT THIELSEN. 
Partly described by Diller in Am. Jour. Sci., 3d ser., vol. 28, p. 257. A hypersthene 
basalt containing hypersthene, olivine, feldspar, and magnetite. In the printed 
paper only the analysis of the groundmass and the fulgurite formed in it are given, 
A. Hypersthene basalt. 
B. Pyroxene. 
C, D. Feldspars. 
E. Groundmass. 
F. A fulgurite, or lightning tube. 
Analyses A and F by F. W. Clarke, record Nos. 108, 105; B, C, D, and E by T.M. 
Chatard, record Nos. 135, 133, 134, 128. These analyses were made early in the 
history of the laboratory and are by no means complete. 
99.39 | 98.11) 100.00 | 100.00 | 100. 23 98. 85 
Iron oxides not separated. Analyses B, C, D, and F made on very small quantities of material. Cand 
D were analyzed by the hydrofluoric-acid method, and the silica was determined by difference. 
2. RIDDLES QUADRANGLE. 
A. Peridotite, the matrix of the silicate nickel ores. Described by Diller and 
Clarke in Bull. 60, p. 21. The rock, which may be classed as saxonite, consists essen- 
tially of olivine and enstatite, with a little chromite and magnetite. Olivine pre- 
dominates, and the enstatite forms less than one-third of the mass. Quartz, serpen- 
tine, and genthite are present as alteration products. 
