MINERALOGY. 107 



The martial mica in a calcining heat acquires 

 a yellow mining colour, which has induced many 

 to examine it for gold-, but nothing can be ob- 

 tained from it except iron, which may be dilTolved 

 or extracted by means of aqua regis : although 

 a late German author has pretended that he pro- 

 duced from the mica an unknown femi-metal, 

 which refembled iron mixed with zink. Never- 

 thelefs he owns, that he has not examined this 

 femi-metal, and that for obtaining it he ufed a 

 flux, compoied of feveral metals, fome of which 

 probably united with the iron in the mica : where- 

 fore it is probable we mall never hear more 

 of it. 



Some of the micaceous kind feem fat and unc- 

 tuous, and others harm and dry : it is not impro- 

 bable that the former may contain a phlogifton, 

 although this cannot be extracted from them in 

 form of a pure oleum talci \ in other particulars, 

 they are fo like one another, that there is no rea- 

 fon for making them two diftincl: genera. 



The talc cubes, as they are called, which have 

 the figure of alum, and are fbmetimes found in 

 the copper-mine of Falun, in the province of 

 Dalarne, and which are very much valued by fome 

 foflilogifcs, are, when broke, found to confift of 

 an iron ore, often mixed with a yellow or mar- 

 chafitical copper ore, and only covered with a 

 very thin coat of mica. 



The tranfparent Mufcovy glafs is ufed for win- 

 dows, and upon all occafions where panes of glafs 

 are wanted. Perhaps it might alfo be advan- 

 tageouily employed to cover houfes. 



The twilled or crumpled mica, which is found 

 at Handol in Jemtland, is there manufactured 

 into kettles and other veiTels, as alfo for hearths 

 of dummies ; and the powder which falls in the 



working 



