302 Elements of Mineralogy. 



to 100 of lead in its metallic ftate. The 

 decanted liquor evaporated to drynefs, af- 

 fords the phofphoric acid. 



SPECIES V. 



Mineralized by Sulphur, with Silver and a 

 little Iron. 



Galena* Potter's Ore, Bley G/anz y Bley Sc&ivetf, 

 of the Germans. 



13. It is the commoneft of all lead ores, 

 of a bluifli dark lead colour, formed of cubes 

 of a moderate fize, or in grains of a cubic 

 figure, whofe corners have been cut off; its 

 texture is lamellar, and its hardnefs variable ; 

 the hardeft fort containing a greater mixture 

 of iron or quartz ; that in grains is thought 

 to be the richeft in filver; but the richeft con- 

 tains only about i or 1,5 per cent, that is, 

 12 or 1 8 ounces per quintal, the pooreft about 

 60 gr. Ores that yield about -| an ounce of 

 filver per quintal, are barely worth the coft 

 of extracting it ; the proportion of fulphur 

 to lead in this ore is alfo variable within the 

 limits of 15 and 25 per cent, that which con- 

 tains leaft is called Bley Sch'weif, and is in 

 fome degree malleable. The proportion of 

 lead is from 85 to 60 per cent, by reafon of 

 an accidental mixture of quartz, that of iron 



is 



