584 REPORT OF NATIONAL MUSEUM, 1890. 



basalt from Snag Lake, near Lassen's Peak, California (No. 38604), is 

 regarded by Mr. J. S. Diller as a product of the latest volcanic eruption 

 in California, and perhaps in the United States (Alaska excepted). 

 This lava field covered an area of only about 3 scpiare miles, and trunks 

 of trees killed at the time of the eruption are still standing. 

 The following localities and varieties are represented : 



Olivine free basalt : Stoppelberg, near Wiensbacb, Rhon Mountains, Prussia, 70254. 



Olivine basalt: Beaver Head County, Montana, 36571; Valmont, Boulder County, 

 Colorado, 36491 ; near Golden, Jefferson County, Colorado, 36674 ; Canadian Hills, 

 New Mexico, 29173 ; Turkey Mountains, New Mexico, 29160; Washoe District, 

 Nevada, 24054 ; Aurora, Nevada, 35477 ; Antelope Spur, Mt. Washburn, Wyoming, 

 29094 ; Madeline Valley, California, 25322; Ten-mile Creek, Quinn River Valley, 

 Oregon, 35350; Gardiner's River, Yellowstone National Park,72858; South of Eigbt- 

 rnile creek, west side of Madison Valley, Madison County, Montana, 72799; South 

 branch Bear Creek, East side Madison Valley, Madison County, Montana (olivine 

 rich variety), 72800; South of Cherry Creek, Madison County, Montana, 72944 ; 

 Agate Pass, Cortez Range, Nevada, 21302; Basalt Hills, Kawsoh Mountains, 

 Nevada, 21998; Uualashka, Alaska, 26076 ; Lehigh River, Victoria, Australia, 

 28193 ; Chatham Islands, Galapagos Archipelago, 70655; Finkeuberg, near Bonn, 

 Prussia, 36496 ; Lowenburg, Jungfernberg, Petersberg, and Oelberg in the Sieben- 

 gebirge, 36490, 36492, 36493, and 36494 ; Unkel on the Rhein (Saulen basalt, near 

 Limburgite), 36495 ; Limburg, Nassau, Germany, 36497 ; Alsfeld, Hesse, Germany, 

 36498; Tannenbergstbal in the Erzgeberge, 36499; Groditzberg, Silesia, 34752 ; 

 Auvergne, France, 35858, San-Miguel, Azores Islands, 35522 and 35524; Zaca- 

 tecas, Mexico, 37782 and 37786; Serena, Mexico, 37701 ; Disco Island, Greenland 

 (with native iron), 12118; Thordarfell, Reykjavir, Iceland, 72807 ; Hawaiian 

 Islands (rich in olivine) 35852. 



Quartz basalt : Near Snag Lake, Lassen's Peak, California, 36604. 



Hornblende basalt : Rossdorf, Rhon Mountains, Germany, 70264. 



Hyalobasalt — Tachylite : Hilo, Hawaiian Islands, 70567 ; Kilauea, Hawaiian Islands, 

 (PelesHair), 72947; Gethurms, Vogelsberg, Prussia, 70261 and 70263; Eossdorf, 

 Silesia, 70677. 



10. The tephrites and basanites. 



Mineral composition. — The essential constituent of the rocks of this 

 group as given by Eosenbnsch are a lime-soda-feldspar and nepheline 

 or leucite, either alone or accompanied by augite. Olivine is essential 

 in basanite. Apatite, the iron ores, and rarely zircon occur in both 

 varieties. Common accessories are sauidin, hornblende, biotite, hauyu 

 (see specimen 34086 from Niedermendig), melauite, perowskite and a 

 mineral of the spinel group. 



Chemical composition. — The following is the composition of (I) a nephe- 

 line tephrite from Antao Pico da Cruz, Azores, and (II) a nepheline-ba- 

 sanite from San Antonio, Cape Verde Islands, as given by Both.* 



*Abhandluugen der Konig. Akad. der Wissenschaften zu Berlin. 1884, p. lxiv. 



