Larsen and Hicks — Searlesite, a new mineral. 437 



Art. XXXY. — Searlesite, a new mineral; by Esper S. 

 Larsen and W. B. Hicks.* 



Introduction. 



In the course of the microscopical study of a number of 

 samples from the old Searles deep well at Searles Lake, San 

 Bernardino County, California, by Mr. Larsen, several minerals 

 were found which could not be determined optically. A 

 chemical analysis of one of these showed it to be a hydrous 

 borosilicate of sodium, and the name Searlesite is proposed 

 for the new mineral after Mr. John "W. Searles, the pioneer 

 who put down the deep well from which the specimen came. 

 The authors wish to express their thanks to Mr. Hoyt S. Gale, 

 of the United States Geological Survey, for his generosity in 

 furnishing the material for this study. 



Occurrence and association. — A sample washed from the 

 clay at a depth of 540 feet, according to the label, was made 

 up almost entirely of nearly white spherulites about a millimeter 

 in diameter. From a microscopic examination these were 

 found to be made up chiefly of the new mineral, searlesite, in 

 minute, fairly well-formed, radiating fibers. Small grains of 

 sand were enclosed in some of the spherulites and nearly all 

 contained much calcite in minute grains or crystals. In 

 addition, a little halite was recognized. The sand grains 

 consisted of quartz, orthoclase, microcline, plagioclase, chlorite, 

 and green hornblende. Searlesite was also recognized in a 

 specimen marked 540' "runnings". This specimen is in 

 massive fragments several centimeters across and is made up 

 chiefly of pirssonite, with some halite, trona, searlesite, sand 

 grains, clay-like material, etc. 



Physical properties and pyrognostics. — The physical pro- 

 perties of searlesite could not be determined accurately on 

 account of the character of the material. It is known, how- 

 ever, that the mineral is rather soft and fuses below red heat 

 to a nearly clear glass. It is readily decomposed by hydro- 

 chloric acid and is appreciably soluble in water apparently 

 without decomposition. Its specific gravity could not be 

 determined. 



Optical properties. — The optical properties were measured 

 with some difficulty and the following results are only 

 approximate : 



a = 1-520, y = 1*528. Optically — (?) 2E = very large 



*Published with, the permission of the Director of the United States 

 Geological Survey. 



