PORPHYRY. 
GENERIC CHARACTER. 
A hard compound stone of various colours. 
AGATE. 
SPECIFIC CHARACTER. 
Porphyrius Achates. P. ex jaspide, quartzo fragili, crystallo, 
amethysto, clialcedonio genuino, cor- 
neolo et onyche, petrosiliee, pyroma- 
cho, pluribus vel paucioribus simul 
compositus. Linn. Syst. Nat. Gmel.3. 
p. 237. no. 66. 
Formed of jasper, brittle quartz, crystal, 
amethyst ; genuine chalcedony, cor- 
nelian and onyx, petrosilex, and com- 
mon flint, mixed together in a greater 
or lesser proportion. 
Achates durissima fere pellucens, diver- 
sis coloribus nitens, variegata. Waller. 
Miner. 84. & Syst. Miner. 1. p. 284. 
no. 22. 
Agate Cronst. Miner. 1. p. 186. Kirwan, 
Miner. 1. p. 330. Patrin, Hist, des 
Miner. 2. p. lpO. Brogn. Miner. I. 
p. 296. 
The agate is in its texture nothing but a flint va- 
riegated with different colours, of sufficient beauty 
