254 



Scientific Proceedings, Royal Dublin Society. 



STEATITE AND PYE.OPHYLLITE. 



[Steatite and pyrophyllite generally occur more or less deteriorated as the rocks, — steatyte 

 (soapstone), and pyrophyllyte (camstone). They are very much confused in the records, 

 both nearly invariably being called by the first name. Steatyte is for the most part 

 made up of silicate of magnesia, and nearly invariably occurs as an adjunct of the 

 intrusive rocks; although in some cases a "fault rock," made up of the debris of 

 intrusive rocks may become a steatyte. They may pass into talcyte. The rock 

 pyrophyllyte, is for the most part made up of silicate of alumina, and nearly always 

 occurs in beds, as if it was a methylotic sedimentary tuffose rock. Nearly invariably 

 it has a fibrous or elongated prismatic structure, and often passes into sericyte, or 

 anhydrous micalyte. 

 The largest and most valuable recorded Irish localities for steatyte are in the Co. Mayo ; 

 while pyrophyllyte is more known in Donegal than any other country. Beds of 

 steatitic clay, or " Fuller's earth" are found in different places, and formerly were 

 much used for abstracting grease from woollen articles, while in the Co. Galwaytbey 

 are still used for that purpose. Pyrophyllyte has been used in the manufacture of 

 lubricators, but as it contains about 30 units of alumina, it might possibly also be 

 utilized in the manufacture of alum and alumina. Neither steatyte nor pyrophyllyte 

 have been carefully looked for or recorded. The following list, therefore, may fall 

 considerably short of the number of places in which they occur.] 



