264 Elements of Mineralogy, 



ii. Dr. Fordyce, in the PhilofophicalTranf* 

 affions for 1780, fuggefts an improvement, 

 by firft diffolving the ore in nitrous acid, and 

 precipitating it by a fixed alkali (if this fo- 

 lution be boiled, any iron it may contain will 

 be precipitated) the precipitate he re-diflblves 

 in vitriolic acid, and precipitates it with 

 iron, 



22. The proportion of fulphur may be 

 found by diffolving the ore in dilute aqua re-* 

 gia, as the fulphur will remain undiffolved. 



SPECIES V. 



Mineralized by Sulphur, 'with 20 -or 30 per 

 cent, of iron. 



Azure Copper Ore, Kupfer Lazur, Kupfer 

 malm. 



23. This differs from the foregoing only 

 in containing more iron; its colour confiftsin 

 various {hades of blue, or reddifh blue j it is 

 as hard, and much more brittle ; it contains 

 from 40 to 60 per cent, of copper, from 20 

 to 30 of iron, and the remainder fulphur ; 

 the poorer it is in iron, the richer in copper j 

 it has been by many confounded with in- 

 durated mountain blue^ 



SPECIES VI. 



