364 DR T. THOMSON on Asbestus, Chlorite, and Talc. 



2MS+/ 2 S. 



LiJii ufi'io JI.S..J .'. :ti-y>JSV 



In the present state of our knowledge we cannot avoid con- 

 sidering rock-wood as a distinct species. All my specimens of 

 rock- wood being from the same locality as the one subjected to 

 analysis, no farther light would have been thrown upon the sub- 

 ject, by multiplying analyses. 



6. Mountain-Leather. 



The specimen of this well known mineral, which I selected 

 for examination, was from the lead-mine of Strontian, where it is 

 pretty frequently met with. The colour was light buff. It was 

 composed of exceedingly fine flexible threads, felted together 

 like a hat, and not capable of being separated from each other. 



Feel very soft ; quite flexible, but tough ; imbibes water 

 very readily, and then assumes very much the appearance of wet 

 leather. 



Opaque, 



Specific gravity 1 .334. 



Before the blowpipe, curls up and fuses easily into an opaque 

 bead. Fuses with carbonate of soda into a transparent yellow 

 bead. Melts with borax into a colourless transparent glass. 



Its constituents were found, by two very careful analyses, to 

 be the following : 



Silica, 51.650 



Alumina, ... 9.505 



Lime, . ... . ., ... . . 10.005 



Magnesia, 2.065 



Protoxide of iron, with some manganese, . 5.805 

 Water, .,'.... 21.700 



100.730 



