452 KEFOET UNITED STATES GEOLOGICAL SUEVEY. 



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

 Hydroplmne, Grand Canon of Yellowstone. 

 Wood opal, East Fork of Yellowstone Eiver. 



Eyalite, in the. Grand Canon of the Yellowstone ; at the Gibbon Geyser Basin. 

 Fealite, at Gibbon Geyser Basin, where it is associated with Hyalite; near the 

 Grand Geyser and Black Sand Geysers, in the Upper Fire Hole Basin ; near 

 the Union Geyser and Yellow Crater Spring, in the Shoshone Basin; on 

 Witch Creek, in the Heart Lake Geyser Basin. 

 Geyserite (fierite or siliceous sinter). In the Geyser Basins of Fire Hole Eiver, 

 presenting white, gray, greenish, pink, and red varieties, massive, porous, 

 filamentous, compact, 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, and Lewis Lake; in the Heart 

 Lake Geyser Basin, on Witch Creek ; in Hay den's Valley, and wherever sili- 

 ceous hot springs are found in the Park. 

 Pealite. (See Opal.) 

 Plasma. (See Quarts.) 

 Prase. (See Quartz.) 



Pyrite (iron pyrites). On Clarke's Fork of the Yellowstone Eiver. 

 Quartz. Bock-cnjsial, in geodes, with chalcedony and calcite, from East Fork of Yel- 

 lowstone Eiver. 

 Amethystine {amesthyst), 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 summit of a bold hill on 

 the south side of the river. 

 Bine, near second canon of the Yellowstone. 



Millcy, near second canon of Yellowstone ; East Fork of Yellowstone Eiver. 

 Chalcedony, in chips throughout the Yellowstone Valley ; in geodes with cal- 

 cite and quartz, above second canon in Yellowstone Valley ; associated 

 with jasper from Elk Creek, near Yellowstone Eiver, Montana Territory; 

 formijttg the outside of geodes from East Fork of Yellowstone Eiver; also 

 associated with calcite at same locality, from Grand Canon of Yellowstone 

 Eiver; in rounded pebbles on shores of Yellowstone Lake. 

 Carnelian, from Grand Caiion of Yellowstone. 

 Chrysoprase, East Fork of Yellowstone Eiver. 

 Prase, East Fork of Yellowstone. 

 Agate, in Yellowstone Valley, above second canon ; East Fork of Yellowstone 



Eiver, near Elk Creek, Yellowstone Valley. 

 Flint (black variety), East Fork of Yellowstone Eiver. 



Jasper (red variety), Yellowstone Valley ; back of East Fork of Yellowstone 

 Eiver ; near Elk Creek ; (yellow variety) East Fork of Yellowstone Eiver ; 

 (gray variety) East Fork of Yellowstone; (green variety) East Fork of 

 Yellowstone Eiver; (black variety) East Fork of Yellowstone Eiver. 

 Silicified wood, abundant throughout the valleys of Yellowstone, and in the 

 Geyser Basins; on the southeast shore of Yellowstone Lake; handsome 

 specimens are found on the East Fork of the Yellowstone Eiver. 

 Sanidine. {^qq Feldspar.) 

 Selenite. (See Gypsum.) 

 Silicified wood. (See Quarts.) 



Sulphur. In crystals at Mammoth Hot Springs of Gardiner's Eiver; in the bluff on 

 Yellowstone Eiver, opposite Tower Falls; in mud springs at the foot of 

 Mount Washburne ; at Crater Hills, in Hay den's Valley ; in small quan- 

 tity in the Gibbon Geyser Basin and in the Lower Fire Hole Basin ; in the 

 Shoshone and Heart Lake Geyser Basins; on the divide between Yellow- 

 stone Eiver and the East Branch of Fire Hole Eiver. 

 Travertine (calcareons tufa). At the Mammoth Hot Springs of Gardiner's Eiver; at 



Soda Butte, on the East Fork of Yellowstone Eiver. 

 Viandite. In the various Geyser Basins of the Park. 

 "Wood opal. {See Opal.) 



