( 1554 ) 
jpart of *em was white, and another a little lower in the 
fame Stone a dark grey, and that they are brought to us 
in little pieces, the biggeft not exceeding a joint of ones 
Finger, and that in fome few pieces there were little ca- 
vities or breaches, wherein I never met with any Metal, 
either of Gold or Silver Tfor in that Mineral there is no 
other) but oftentimes with very fmall Cryftals 5 I call 
them fo, bacaufe of the analogy of their Figures with 
tltofe of Rock- Cryftal, for like them they are tranfparent, 
hexangular, and end in a point or fpire. 
Thefe Cryftals were in the white part ot the Stone, 
for thofe that were in the gi ey were not pellucid. 
I caufed a (mall particle of fuch Cryftal,fo as it appeared 
thro my Glafs, to be defigned by the Limner, and Fig. 9. 
R S T V reprefents it as bright and clear as ever you (aw 
any Cryftal 5 I have feen fome that were not near fotranf- 
parent, but indeed they were taken out of Mineral ftones 
that were of a dark grey colour. 
Some are apt to believe that thefe CryftaU are form*d 
by the exhaling damps or moifturcs deep in thofe Mines, 
from whence the Mineral ftone is dugs but this is con- 
trary to my fentiments, for upon that hypothe(is, the 
whole cavities fhould be (ilfd with the particles, whereas 
we find the contrary, for I h^ve obferv'd that not one 
fourth part of the cavities are filled therewith 5 and I 
have found fome of the faid Cryftals in fuch fmall cavities 
that a pins head would have filfd them, and in breaches 
of the Mineral ftone that were not fo broad as a fmall 
pin is thick, whereas I could meet with none of thefe 
Cryftals in other cavities that were much larger. 
I will rather fuppofe that mod of the ftony matter 
where thofe cavities are found, was of the fame configu- 
ration as the faid Cryftals, and at the fame time of the 
coalition or union of the particles oi Stone, the intercepted 
Air occafioned f6rne cavities, in which the Cryftals were 
fliut up, and in which they acquired the figure which they 
now 
