54 
A SYSTEM OF 
cockle-fpar % of which colour we likewife 
find cockle, or fliirl, in the ifiand of Uto, 
near Stockholm, and at Norbery, in the 
proyince of Weftmanland. 
Mr. Maillet informs us, that in former 
times the beft emeralds were found in 
Egypt f. 
' SECT. XLIX. 
Cbfervations on the preceding bodies called, 
precious-ftones, or gems. 
I have before mentioned the reafons, why I 
give thefe their feparate places from the following 
* The oi igmalSwedifh has Sh'orl fpat^ that is cockle or Ihlrl 
fpar, of which fee fully Se£l. Ixxiii. infra, but the German 
tranflation terms it, ein Schoen /pat, a fine fpari that is to 
fay, (in this fen fe) a fine fluor. The fchorl, or fchirl, of the 
Germans, is a fubfiance called by our Cornilli miners 
Cockle. I have therefore in my le^lures on follils adopted the 
names of cockles or Ihirls for this iubftance in the EnglilH 
language, D. C. 
t The emeralds, in their rough or native flate, con fill 
of hexagonal columns, moftly truncated at both ends, though 
feme of them now and then may be found facetted at the 
ends. I have famples of both tranfparent grafs-green, and 
light green, which in a gentle heat become colourlefs, but 
white and opaque in a llrong lire, without the lead mark qf 
any fufion. 
When criflallifed cockle, or ihirl, is found of a green 
colour, tranfparent, and free from cracks or daws, it is 
commonly called emerald by the jewellers, though it is ge- 
nerally of a deeper colour than the true emeralds, and alfo 
wants its luflre ; and hence it is, that the cockle-fpar from 
Egypt is called the mother of the emeralds. 
However it may be, that this cockle was in antient times 
faliiioaablc in Egypt, under the name of emerald, though 
now-a'days it is not fo much valued as the emerald of this 
(the filicvous) kind. See Section Ixxv, Note under ihe 
cockle. 
flo.nesj 
