406 EEPORT UNITED STATES GEOLOGICAL SUEVEY. 



Table of analysis of travertines or calcareous tufas. 



Locality. 



Analyst. 



CO3 



SiOa 



HaO 



AI2O3 



re203 



CaO 



Manmoth Hot Springs of Gardiner's 



Kiver, Yellowstone National Park. . 



Do 



Endlich 



30.35 



3.32 



1.75 

 0.3 



"T26' 



3.31 



"'6.'22 



0.26 

 2.54 



3.62 

 1.05 



57.70 

 54.2 



Spring near Medway, in TJtati 



Grass Valley Spring near Bardmass 



Woodward . 



do 



do 



41.73 



39.07 

 38.52 



2.49 



8.70 

 6.90 



53.22 



48.32 



Tufa Dome in Pyramid Lake, Nevada. 

 Steamboat Spring on Bear Eiver, 



47.48 





5.98 





92. 55* 











Locality. 



Analyst. 



MgO 



NaaO 



KO 



POi 



SO4 



Totals. 



Mammoth Hot Springs of Gardiner's. 



Kiver, Yellowstone National Park.. 



Do 



EndUch 



Leifmann . . . 

 Woodward . 



do 



do 



Trace. 

 Trace. 



Trace. 









100. 05 









97.10 



Spring near Medway, in Utah 



Grass Valley Spring near Bardmass 









2.38 



100. 00 



3.98 

 2.50 



0.42* 









100. 33 



Tufa Dome in Pyramid Lake, Nevada. 

 Steamboat Spring on Bear Kiver, 



0.48 



0.19 



Trace. 



Trace. 



99. 81 

 100. 00 

















•From Fremont's Keport. 

 SILICEOUS SINTEK. 



Siliceous sinter, tiorite, or geyserite, as the siliceous deposits of ther- 

 mal waters are variously called, is abundant in most of the spring locali- 

 ties of the park, especially in the geyser basins of Fire Hole Eiver. 



Fiorite, the name given by Thompson to the pearly siliceous deposit 

 from near Santa Flora, in Italy, has the priority. The deposits, however, 

 are so characteristic of the regions that Geyserite, the name given by those 

 who first analyzed specimens from Iceland, has been most frequently 

 used. No matter which name is used, fiorite or geyserite is a variety 

 of opal, and in it, perhaps, is to be seen the condition of first stages of 

 the more typical opals, A careful study of the various geyserites, 

 especially the older specimens, found in the geyser basins of the Yel- 

 lowstone National Park, will probably throw light on the subject of the 

 formation of opal. In the Heart Lake Basin I found a geode, the out- 

 side of which was a hard geyserite (Pealite), while the interior was filled 

 with semiopal. In the Iceland region (at Haukadal), chalcedony was 

 found by Descloizeaux in clay, and he was of the opinion that opals and 

 chalcedonies found in some ancient volcanic districts might have had 

 their origin in a similar way. 



According to Bischof, opal may be compared to a solidified mass of 

 gelatinous silica, in which, according to the extent of desiccation, the 

 amount of water may vary much. He also says that the occurrence of 

 opal in fissures shows that it has been deposited from water. Hydro- 

 phane, a translucent light-colored opal found in Saxony, is said to be so 

 soft m the mine that it will receive the impression of a hard substance. 



In the Yellowstone National Park we find first the silica in solution in 

 the hot waters, next the form of gelatinous silica, as in the specimen de- 

 scribed under the name of Yiandite, examined by Mr. Goldsmith. Next 

 to this come geyserites of all textures, some being very soft, especially 

 those recently deposited. Where the deposits are older they are harder 

 and grade into PealiteSj a subvariety named in 1872 by Dr. F. M. End- 

 lich, and placed by him between quartz and opal. Hyalite is also found 

 in the Gibbon Basin in connection with Pealite as an alteration of the 



