Mineralogy. iit 
4. of an oftoedrsl figure. 
a. Clear, colourlefs. This I have jfeeii 
in the colleftion of the mirie-maftef 
Mr. Von Swab. 
SECT, CL 
Obs ervation on the Fluor s. 
There are not yet any probable reafons given, 
why thefe Hones ihould be ranked amongll the 
calcareous or any other earths *, and if I am not 
quite miftaken in my judgment, they are fo 
much the more difFerent from the calcareous 
earth, as they, when melted together with it, pro- 
duce an effedc which never can be aferibed to the 
alcaline earths ; not to mention, that there is by 
no method yet known any calcareous fubfiance to 
be extra6bed from them, nor is there any pofli- 
bility of decompounding them. 
That which caufes the phofphorefcent light 
vanilhes in the fire, it being impoflible to cbllefl: 
it : in the prefent ignorance of the nature of this 
matter, it cannot therefore be alTerted, whether it 
is one of the conftituent parts neceffary to the 
compofition of thefe Hones, or if, in regard to 
its fmall quantity, it even .deferves any attention. 
I take it to be a fubtle phlogiHon, which being 
modified in various manners, gives rife to fuch 
various colours. 
At mineral works this kind of ftone is very ufe-^ 
fill in promoting the fufion of the ores, and is 
therefore as much valued by the fmelters, as the 
borax is by the effayers : it has alfo from this 
quality got the name of fnior, or flux. 
The refemblance between the coloured fluors, 
^nd the compofitions made of glafs, has perhaps 
contributed 
