86 <?be Rufy, Sapphire, &c. [Book VI. 



purple. 2. The fpinell ruby, of a ponceau red, that is, 

 of a bright cofn-poppy-flower colour. 3. The balafs- 

 ruby, pale red inclining to violet. 4. The rubicell, 

 of a reddifh -colour. 



3. The fapphire is tranfparent, and of a blue colour, 

 and is faid to be next to the diamond in hardnefs. They 

 are fomttimes of a milky appearance. 



4. The topaz is chiefly of different fhades of yellow, 

 but is fometimes greemfh. When of a fea-green co- 

 lour it is called aqua- marine; when more green, the 

 beryl ; when yellowish green, the chryfolite. 



5. Emerald, the chief colour of which is green, is the 

 foft^lr of the precious ftones, and when heated is phof- 

 phortfcent like the fluors. 



6. The jacinth or hyacinth, is of a fine reddifh yel- 

 low colour, and fometimes brown ; thefe gems are 

 formed in prifms, pointed at both ends. 



7. The amethyfl is a gem of a violet colour, or 

 great brilliancy, and as hard as the beft kinds of rubies 

 and fapphires, from which it only differs in its colour. 

 This is called the oriental amethyft, and is very rare ; 

 when it approaches to the purple, or rofe colour, it is 

 more eileemed than when it inclines to the blue. 



The amethyfts called occidental, are of the fame 

 nature as rock cryftals, and have the fame gradations 

 of colour. Cryftals within the geodes, or hollow agate- 

 balls, are very often found of an amethyft colour, and 

 fome are very fine. 



8. The garnet, when tranfparent and of a fine co- 

 lour, is reckoned among the gems ; but it varies more 

 than any, both with refpect to its form and colour, fome 

 being of a deep and dark red, fome yellow and purple, 

 and fome brown, blackilh, and quite opake. The 

 regular fhape of the garnet is the dodecagon, with 

 rhomboidal faces, and its chief variation is, die double 



i eight- 



