TALCOSE SCHIST. 109 



is indicated hy the presence of steatite, foliated talc, 

 and asbestos. As accompanying that rock, it gene- 

 rally forms the boundary between it and the schistose 

 strata in which it happens to lie ; seeming to be abun- 

 dant only when they consist of micaceous schist. 

 When the including rock is gneiss, it often unites 

 with that, so as to form a talcose gneiss, noticed in 

 the Classification. I know not that it occurs con- 

 spicuously in argillaceous schist ; but minute laminae 

 of it are occasionally found, producing that talcose 

 surface which this sometimes presents on splitting. 



This rock is the repository of many well-known 

 minerals ; but if too limited to be largely metalli- 

 ferous, it contains Chroinat of Iron in Shetland. As 

 a building stone, its harder varieties have been advan- 

 tageously used in Scotland; while the facility of 

 shaping it, and its apparent indestructibility, entitle 

 it to the notice of architects. Though recommended 

 for furnaces, it has always proved to be very fusible 

 in my own trials. Because sometimes used for ves- 

 sels, it has been called potstone ; to the no small 

 confusion of the nomenclature, among careless mine- 

 ralogists. 



