NOME II. D. PORPHYRY. 239 



been made even by skilful mineralogists, while 

 he repeatedly informs us himself that it is a grey 

 argillaceous stone, mistaken by the miners for a 

 sandstone, often containing crystals of felspar 

 and quartz, and sometimes schorl. But in gene- 

 ral the felspar itself seems to be decomposed, 

 forming oblong white spots on the grey base. 

 The gold and the opal would appear to have 

 been formed after the decomposition of the rock. 

 Opal and chalcedony are also found in entire 

 porphyry; as well as veins of gold. The various 

 porphyries of the German writers, occasion a 

 strange confusion in the very nature of the sub- 

 stances. 



The saxum metalliferum might as well be Bomite. 

 called Bornite, in honour of that great mine- 

 ralogist. 



HYPONOME I. 



Bornite, from various parts of Hungary. 



Micronome 1. The same, with native gold in 

 thin plates and disseminated, from the same. 



Micronome 2. The same, with sylvanite, from 

 Nagyag in Transilvania. 



Micronome 3. The same, with fine dendritic 

 gold, from Cremnitz in Hungary. 



