Siliceous Genus. 1 1 9 



according to Mr. Achard, 41,33 of argill, 

 21,66 of filex, 20 of calcareous Earth* and 

 13,33 of iron. 



Hyacinths are found in Poland^ Bohemia^ 

 and Saxony. 



III. VARIETY. 

 Green. 



Emerald, Chryfolite, Beryl. 



The colour of emerald is pure green ; it is 

 fometimes found in round flat pieces, but 

 moftly cryftalized in hexagonal prifms ; its 

 fpecific gravity is from 2,78 to 35711. It is 

 the fofteft of all the precious ftones. 



According to Mr. Achard, it preferves its 

 colour in a porcelain heat, and only becomes 

 more opake ; in a ftronger heat it melts into 

 a flag. Mem. Stock. 1768. Like the fore- 

 going it eludes the force of mineral alkali, 

 but yields to borax and microcofmic fait. 

 With the former, according to Mr. Qulft-> it 

 gives a colourlefs gl,afs. 



100 parts of it contain, by Mr. Bergman** 

 analyfis, 60 of argill, 24 of filex, 8 of cal- 

 careous Earth, and 6 of iron j and by that of 

 1 4 Mr, 



