mineralogy. io; 
The martial mica in a calcining heat acquires 
a yellow fhining colour, which has induced many 
to examine it for gold •, but nothing can be ob- 
tained from it except iron, which may be dilfolved 
or extraded by means of aqua rcgis : 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, compofed of feveral metals, fome of which 
probably united with the iron in the mica ; where- 
fore it is probable we fliall never hear more 
of it. 
Some of the micaceous kind feem fat and unc- 
tuous, and others harfh and dry : it is not impro- 
bable that the former may contain a phlogifton, 
although this cannot he extraded from them in 
form of a pure cletm talci ; in other particulars, 
they are fo like one another, that there is no rea- 
fon for making them two diflind genera. 
The talc cubes ^ as they are called, which have 
the figure of alum, and are fometimes found in 
the copper-mine of Falun, in the province of 
Dalarne, and which are very much valued by fome 
foflilogifiis, are, when broke, found to confifl: 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 Mufcpvy glafs is ufed for win- 
dows, and upon all occafiOns where panes of glafs 
are wanted. Perhaps k might alfo be advan- 
tageoufiy employed to cover houfes. 
The twifted or crumpled mica, which is found 
at Handol in "jemtland, is there manufadured 
into kettles and other veflTels, as^alfo for hearths 
of chimnies ; and the powder which falls in the 
working 
