450 Mr. Thomas Richardson s [June 



The quantity of tungstic acid was determined from the 

 loss, which prevents us from placing so much confidence in 

 it as we could otherwise have done, from the known dexte- 

 rity and precision of the analyst. 



This mineral occurs generally along with tinstone, in 

 veins and beds ; it is met with also traversing greywacke, 

 with ores of lead, &c. It is found in almost all the Saxon 

 and Bohemian tin mines, as also in several places in 

 Cornwall. 



It is thus found in France : In Siberia it occurs accom- 

 panying the emerald, and also in the United States of 

 North America. 



It occurs massive, and often crystallized. The primary 

 form being a right oblique angled prism. The specimen 

 subjected to analysis was from Zinnwald, in Bohemia, and 

 seemed perfectly pure. 



It possessed the following characters : — 



Foliated; not very brittle; fracture uneven; streak, 

 reddish brown ; colour, blueish black ; lustre, approaching 

 metallic; opaque; hardness, 5*0 to 5*5; sp. gr. 7*017. 



Before the blowpipe, decrepitates when heated alone, 

 but may be melted in a high temperature into a globule, 

 possessing the metallic lustre. 



With soda, on platinum wire, it fuses into an opaque green 

 coloured bead in the oxydizing flame, which changes to 

 pink in the reducing flame : with borax fuses easily into a 

 transparent red coloured bead in the oxydizing flame, which 

 becomes pale yellow in the reducing flame. With salt of 

 phosphorus fuses readily into a transparent yellow coloured 

 bead in the oxydizing flame, which becomes red in the 

 reducing flame. On adding a small piece of tin to this red 

 coloured bead and continuing the flame for a short time the 

 colour changed to green. 



It was analyzed in the following way : — 



A. 20. grs. of the mineral, in fine powder, were kept 

 fused with 60 grs. of carbonate of soda (anhydrous) for half 

 an hour. The whole, upon cooling, was digested in water 

 for 48 hours. The insoluble portion which remained be- 

 hind was separated by a filter, and well washed with distilled 

 water. The solution which came through the filter, together 

 with the washings, being evaporated to a convenient bulk, 



