54 A SYSTEM OF 



cockle-fpar *, of which colour we likewiie 

 find cockle, or fhirl, in the ifland of Uto, 

 near Stockholm, and at Norbery, in the 

 province of Weftmanland. 



Mr. Maillet informs us, that in former 

 times the befl emeralds were found in 

 Egypt f . 



SECT. XLIX. 



Obfervations 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 original Swedifh has Skiorlfpat, that is cockle or fhirl 

 fpar, of which fee fully Sett, lxxiii. infra, but the German 

 tranflation terms it, ein Schoen /pat, a fine fpar ; that is to 

 fay, (in this fenfe) a fine fluor. The fchorl, or fchirl, of the 

 Germans, is a fubftance called by our Cornifh miners 

 Cockle. I have therefore in my lectures on foffils adopted the 

 names of cockles or fhirls for this fubrlance in the Englifh. 

 language, D. C. 



t The emeralds, in their rough or native ftate, con fid 

 of hexagonal columns, moflly truncated at both ends, though 

 fome 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 firong fire, without the leaft mark of 

 any fufion. 



When crlftallifed ccck'e, or fhirl, is found of a green 

 colour, tranfparent, and free from cracks or flaws, 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 luftre : 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 

 f^miooable in Egypt, under the name of emerald, though 

 now-a-days it is not fo much valued as the emerald of this 

 (the filiceou;) kind. See Section Ixxv. Note under the 

 cockle. 



flones, 



