Chap. 32.] 1'urqtiolfe Storit. 193 



and is volatilized partly in the metallic ftate. Copper, 

 in a heat far lefs than is fufficient to melt it, becomes 

 calcined at its furface, and exhibits various colours. In 

 a greater heat than is fufHcient to pro luce this effect, 

 its furface is converted into thin fcales, which mav^ be 

 eafily fcraped off. 



Copper is fometimes found native, having the me- 

 tallic fplendor, the malleability, and all the properties 

 of ordinary copper, It has fometimes the form of 

 plates, fometimes that of fibres or branches, and is 

 fometimes cryftallized. Copper, in its metallic ftate, 

 is fometimes found depofited on ores of iron, in which 

 cafe it muft be confidered as having been feparated 

 from native vitriol of copper by the fuperior attraction 

 of iron for the vitrioii., ne native folutions 



of copper often depofit that metal in a calcined ftate 

 in beds of calcareous earth. The turquoife ftone 

 is the tooth of an animal, penetrated with the blue 

 calx of copper. Copper is generally found, how- 

 ever, in ores. Thefe are frequently mineralized by 

 fulphur. What are improperly called the vitreous 

 ores of copper are of this kind j they are brown, red } 

 and grey, and thefe colours are frequently mixed with 

 a greenifh or violet tinge. Thefe melt eafily, are 

 very ponderous, may be fcratched or even -cut with 

 a knife, and are very rich in metal, as an hundred 

 pounds of them ufually yields from eighty to ninety 

 of copper. The azure copper ore differs from the 

 former chiefly in containing a confiderable quantity of 

 iron. The grey copper ores, which have not much 

 fplendor, confiit of copper, fulphur, arfenic, and f ;me 

 iron. What are called copper pyrites contain in 

 reality more iron than copper, but yield enough of the 

 latter metal to anfwer the expence of working them; 



VOL, II. , O they 



