MINERALOGY. €& 



which it fo nearly refembles* that it is not 

 eafy to point ot:t fuch characters as fhall rea- 

 dily diftinguiih it from them. The beft 

 way, perhaps, will ht tc fpeak of its pro- 

 perties comparatively > and then we may faj 

 that, 

 i. It is more uniformly folid, and not fo 



much cracked in the huafs as the quartz 5 



and, 

 '2. It is more pellucid than the jafper. 

 0. It bears being errpofed to the air, without 



decaying, better tkan the jafper, but not 



fo well as the quartz. 



4. It is better for making of glafs than the 

 jafper, but is not quite fo good as quartz 

 for that purpofe. 



5. When ever there has been an opportu- 

 nity in this matter of its mooting into 

 criftals, quartz criftals are always found 

 in it ; jure as if the quartz had made one 

 of its conftituent parts, and had on cer- 

 tain circumftances been fqueezed out of 

 it ; this is to be fcen in every hollow 

 flint, and its clefts, which are always rilled 

 up with quartz. 



6. It often fhews moft evident marks of 

 having been originally in a foft and ilimy 

 i re. 



The feveral varieties of this fpecies 

 have obtained diftincl names, more with 

 refpect to their colours, than from any 

 real rence in their fubftance'-, but 



thefe are ftill neceiTary to be retained, as 

 the only names ufed bv jewellers and 

 others, who know how to value them ac- ; 

 cordingly. 



SECT, 



