GEOLOGICAL SUEVEY OF THE TERRITOEIES. 181 



ifephelite. In trachytes in Grand Canon of Snake Eiver, Idaho Territory. 



Obsidian, (volcanic glass.) On Trail Creek, near Yellowstone Valley; 

 in chips throughout the Yellowstone Valley, from the lower caCon 

 to Yellowstone Lake. Spherulitic, from Grand Canon of Yellowstone 

 Eiver. Poi-phyritic, froui Grand Cailon of the Yellowstone ; divide 

 between Yellowstone and Madison Elvers; Yellowstone National 

 Park; east side of Snake Eiver, Idaho Territory ; in basin of Henry's 

 Lake, Idaho Territory ; head of Falls Eiver, Idaho Territory; Lewis's 

 Lake, Wyoming Territory ; valley of Madison Eiver, Montana Terri- 

 tory ; WestGallatin CaQon, Montana Territory ; near Missouri Eiver, 

 below Horseshoe Bend, Montana Territory. 



OKvine. In basalts in Yellowstone Valley, opposite Boteler's Eanch, 

 Montana Territory; in basalts on Snake Eiver and Henry's Fork, 

 Idaho Territory. 



Opal. East Fork of Yellowstone Eiver, Grand Canon of Yellowstone ; 

 summit of Mount Blackmore, Montana Territory ; Colorado Springs, 

 Colorado Territory. Hydrophane, Grand CaQon of Yellowstone. 

 Wood-opal, East Fork of Yellowstone Eiver, near Gallatin City, 

 Montana Territory ; Jefferson County, Montana Territory. Dendritie, 

 Hot Springs district, Montana Territory. Hyalite, Grand Caiion of 

 Yellowstone Eiver. Excellent specimens ; clear, in colorless globu- 

 lar concretions, from summit of Mount Blackmore, Montana Terri- 

 tory; near Jackson's Lake, Wyoming Territory. Geyserite, (siliceous 

 sinter,) geyser-basins of Fire-Hole Eiver, presenting white, gray, 

 greenish, pink, and red varieties, massive, porous, filamentous, com- 

 pact, cauliflower-like, beaded, or pearly. The specimens vary from 

 translucent to opaque, some being very friable while others are firm, 

 even on drying; Hot Springs, on southwest arm of Yellowstone 

 Lake ; geyser- basin of Shoshone Lake, Yellowstone National Park. 



Plasma. (See Quartz.) 



Prase. (See Quartz.) 



Pummice. Emigrant Gulch, Montana Territory. 



Pyrite, (iron pyrites.) With galena. Central City, Colorado Territory j 

 with serpentine and hematite, near Ogden, Utah Territory; in 

 quartzite, in Emigrant Gulch, Montana Territory ; Clarke's Fork of 

 Yellowstone Eiver, Montana Territory. Pentagonal dodecaliedral 

 crystals, from Teton Mountains, Idaho Territory ; Little Cotton- 

 wood Caiion, Utah Territory. 



Quartz. In granites throughout Eocky Mountains. Bodccrystal, Og- 

 den, Utah Territory ; in geodes, with chalcedony and calcite^ from 

 East Fork of Yellowstone Eiver ; from Sawtelle's Peak, near Henry's 

 Lake, Idaho Territory ; in granites of Teton Mountains, Idaho Ter- 

 ritory ; divide between Eoss Fork and Fort Hall, Idaho Territoiy. 

 Amethystine {amestliyst,) from the Colorado divide south of Denver, 

 Colorado Territory ; fine crystals in large geodes of chalcedony 

 from East Fork of Yellowstone Eiver, about ten miles above the 

 junction of the Yellowstone. The specimens are found on the sum- 

 mit of a bold hill on the south side of the river. Blue., near sec- 

 ond canon of the Yellowstone. Smoky {cairngorm stone,) Colorado 

 divide, Colorado Territory. Millcy, near second canon of Yellow- 

 stone; Eai-t Fork of Yellowstone Eiver. Chalcedony, Spring Caiion, 

 near Fort Ellis, Montana Territory ; in chips throughout the Yel- 

 lowstone Valley ; in geodes with calcite and quartz, above second 

 canon in Yellowstone Valley ; associated with jasper from Elk Creek, 

 near Yellowstone Eiver, Montana Territory ; forming the outside of 

 geodes from East Fork of Yellowstone Eiver ; also associated with 

 calcite at same locality, from Grand Caiion of Yellowstone Eiver; 

 in rounded pebbles on shores of Yellowstone Lake ; from summit of 



