574 REPORT OF NATIONAL MUSEUM, 1890. 



arite from High Rock Canon Nevada (35441), is shown in the colored 

 transparency in the window (39079). Transitions from compact obsidian, 

 into pnmiceous forms, due to expansion of included moisture, are com- 

 mon, as shown in the samples from the Mono Craters in California and 

 those from the Li pari Islands. 



Classification and nomenclature. — The following varieties are now 

 generally recoguized, the distinctions being based mainly on structural 

 features, as with the quartz porphyries. We thus have the granitic- 

 appearing variety nevadite. The less markedly granular and porphyritic 

 variety rhyolite, and the glassy forms hyalolip arite , hyaline rhyolite, or 

 obsidian as it is variously called. Hydrous varieties of the glassy rock 

 with a dull pitch-like luster are sometimes called rhyolite pitchstone. 



The name rhyolite, from the Greek word pew, to flow, it may be stated, 

 was applied by Richtofen as early as I860 to this class of rocks as occur- 

 ring on the southern slopes of the Carpathians. Subsequently Roth ap- 

 plied the name liparite to similar rocks occurring on the Lipari Islands. 

 The first name, owing to its priority, is the more generally used for the 

 group, though Professor Rosenbusch in his latest work has adopted 

 the latter. The name nevadite is from the State of Nevada and was 

 also proposed by Richtofen. The name obsidian as applied to the 

 glassy variety is stated to have been given in honor of Obsidius, its 

 discoverer, who brought fragments of the rock from Ethiopia to Rome. 

 The name pantellerite has been given by Rosenbusch to a liparite in 

 which the porphyritic constituent is anorthoclase. 



The following localities and varieties are now represented : 



Nevadite : Ten Mile District, Summit County, Colorado, 36872 and 36392; Chalk 

 Mountain, Lake and Summit Counties, 73176; Apati, Hungary (Felso-Nevadite) 

 36209. 



Rhyolite : Near Cortez, Nevada, 35361 ; Golanda Canon, Sonoma Range, Nevada, 

 35327 ; south end of High Rock Canon, Nevada, 35357 ; south end of Ha-wa-wa 

 Mountains, Utah, 35308 ; Beaver Head Canon, Montana, 36779 ; south of Cherry 

 Creek, west side of Madison Valley, Madison County, Montana, 72945 ; Mount 

 Sheridan, Wyoming, 38835 ; Yellowstone Canon, Yellowstone Park, Wyoming 

 28829; summit of Flat Mountain, Wyoming, 28843; Pima and Cochiel Counties 

 Arizona, 28578 ; Rattlesnake Hill and Querida, Custer County, Colorado, 36871 

 36868, and 36870 ; Hidalgo, Santa Rosa, Zacatecas and Tezintlan, Mexico, 34995 

 37734, 37689, 37730, and 37987; Bear Creek Falls, Shasta County, California 

 70591; Schemnitz, Eisenhach, Hlinik, Glaskutte, Nagy Tolesva, Kremnitz, Hun 

 gary, 34590, 36263, 36267, 36266, 36264, 36270, 36271, 36265, 36268, and 70122 

 Berkune and Kuckstein, in the Siehengebirge, Prussia, 36261, and 36262. 



Hyalo-liparite; obsidian: Crater south side of Mono Lake, California, 22901 and 22899 

 iWd.(pumiceous forms), 22904 and 22907 ; Mono Lake, 8 specimens showing com- 

 pact and pumiceous forms, 29630, 29631, 37210,37211; same locality, showing 

 spherulites, 35274 ; Upper Pit River, California, 1675 ; Deer Creek Meadows 

 (spherulitic), 38364 ; Glass Buttes, Oregon, 35268 and 35267 ; Coyote Springs.Utah, 

 35265; Beaver Valley, Utah, 35269; obsidian cliffs in the Yellowstone National 

 Park, 10569, 18969, 72855 and 72856; the same locality (spherulitic forms), 18969, 

 28921, 29106, 10574, 29107, 70676, and 28979 ; the same locality, with lithophysaj 

 72852; Obsidian canon, Yellowstone National Park, 28922, 28923, and 10570; 

 between Madison River and Shoshone Lake, Wyoming, 28914 and 28917; south 



