386 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



LATAH COUNTY 



Certain deposits of fire clays resulting from the decomposition of 

 granite and pegmatite which are worked at Moscow and Troy have 

 been described by Soper. 97 These are for the most part residual 

 kaolin containing quartz. 



OWYHEE COUNTY 



Clayey materials are of very frequent occurrence in the Silver City 

 district. Chemical investigation has shown that these vary some- 

 what in composition, some having the composition of pure kaolin, 

 some of pure sericite, and many corresponding to a mixture of the 

 two minerals. These have already been mentioned under sericite. 

 In addition to kolinite and sericite, leverrierite, discussed below, is 

 present in some mines. 



A white clay gouge from the Tip Top vein has a composition inter- 

 mediate between kaolinite and sericite. A "talc" forming the filling 

 of fissures in the Henrietta mine, which was rich in miargyrite con- 

 tained : 



Per cent 



Water (H 2 0) below 100° C 1. 70 



Water (H 2 0) above 100° C 9. 40 



Potash (K 2 0) 1. 86 



Soda (Na 2 0) Trace. 



This may be a mixture of kaolinite and sericite. In the De Lamar 

 mine kaolinite occurs as white chalky or talcose material forming 

 parts of the vein. Sometimes it is a metasomatic replacement of 

 rhyolite. The white "talc" which underlies the "iron dike" in this 

 mine and contains shot and larger masses of argentite (or naumannite 

 q. v.) is apparently pure kaolinite. A specimen from the second 

 level contained: Water 14.12 per cent, potash trace, gold 13.7 ounces 

 per ton, silver 2.30 ounces per ton. Similar material from a veinlet 

 of comb quartz is also probably kaolinite, as it contains no potash. 98 



MONTMORILLONITE AND LEVERRIERITE (492) fl8 ° 



Hydrous aluminium silicate, compo- Monoclinic, clayey, 



sition varying from approximately 

 A1 2 .3Si0 2 .4H 2 to about A1 2 3 . 

 5Si0 2 .7H 2 0. 



There are certain clayey materials which have peculiar properties- 

 which distinguish them from the ordinary clay minerals kaolinite, 

 sericite, and halloysite. Such a clay was described by Wherry and 

 Larsen from a mine in Colorado and for it the name leverrierite was 

 used while the authors consider rectorite, delanouite, kryptotile, and 

 batchelorite as all being the same material. Since then it has become 



87 E. K. Soper. Journ. Amer. Ceram. Soc, vol. 1, pp. 94-98, 1918. 

 «s Waldemar Lindgren. U. S. Geol. Survey, 20th Ann. Rept., pt. 3, p. 171, 1900. 

 •s» It has not been possible to revise the text of this bulletin in accord with recent work on the 

 mineralogy of the clay minerals by Ross and Shannon. 



