GEOLOGICAL SURVEY OF THE TEREITORIES. 181 



JS'ephelite. In trachytes in Grand Canon of Snake Eiver, Idaho Territory. 



Obsidian, (volcanic gla^s.) On Trail Creek, near Yellowstone Valley; 

 in chips throughout the Yellowstone Valley, from the lower canon 

 to Yellowstone Lake. Spherulitic, from Grand Caiion of Yellowstone 

 Kiver. PorphyritiCj from Grand Caiion of the Yellowstone ; divide 

 between Yellowstone and Madison liivers ; Yellowstone National 

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

 Lake, Idaho Territory ; head of Falls Kiver, Idaho Territory; LewiVs 

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

 tory ; West Gallatin Canon, Montana Territory; near Missouri River, 

 below Horseshoe Bend, Montana Territory. 



Olivine. In basalts in Yellowstone Valley, opposite Boteler's Ranch, 

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

 Idaho Territory. 



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

 summit of Mount Blackmore, INIontana Territory ; Colorado Springs, 

 Colorado Territory. Hydrophane, Grand Caiion of Yellowstone. 

 Woodopaly East Fork of Yellowstone River, near Gallatin City, 

 Montana Territory ; Jeiiersou County, Montana Territory. Dendritie, 

 Hot Springs district, Montana Territorj'. Hyalite, Grand Canon of 

 Yellowstone River. 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 River, presenting white, gray, 

 greenish, pink, and red varieties, massive, })orous, 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 Quarts:.) 



Prase. (See Quartz.) 



Pummice. Emigrant Gulch, Montana Territory. 



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

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

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

 Yellowstone River, Montana Territory. Pentagonal dodecahedral 

 crystals, from T6tou Mountains, Idaho Territory ; Little Cotton- 

 wood Canon, Utah Territory. 



Quartz. In granites throughout Rocky Mountains. Roclc crystal, Og- 

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

 East Fork of Yellowstone River ; from Sawtelie's Peak, near Henry's 

 Lake, Idaho Territory ; in granites of T6ton Mountains, Idaho Ter- 

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

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

 Colorado Territory ; fine crystals in large geodes of chalcedony 

 from East Fork of Yellowstone River, 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 caiion of the Yellowstone. Smoky {cairngorm stone,) Colorado 

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

 stone ; Easst Fork of Yellowstone River. Chalcedony, Spring Caiion, 

 near Fort Ellis, Montana Territory ; in chii)s throughout the Yel- 

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

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

 near Yellowstone River, Montana Territory ; forming the outside of 

 geodes from East Fork of Yellowstone River ; also associated with 

 calcite at same locality, from Grand Canon of Yellowstone River; 

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



