ON THE NATIVE SULPHURETS Of IRON. 273 



»ng to 14 or 15 per cent; it is very pofiible, that this metal 

 may in its faturation follow the fame law as iron, which re- 

 quires to be examined; but only in the fulphurets which are 

 pure ; for in thofe which are complicated, or thofe in which 

 the fulphuret of copper is an integrant part, I have found it 

 without excefs of fulphur. n- 



The yellow copper ores, or the native union of the two Copper pyrites, 

 fulphurets of copper and iron fulphu rated to the maximum, arc mixed : their 



' , i i.o-ii • ■ r p i i i i f i • i habitudes, 



afford by diltillation lets lulphur than the fimple pyrites, be- 



caufe the fulphuret of copper in this mixture has no excefs. 



The beautiful copper pyrites of Avalar in Bifcay, affords no 



more than one twelfth of fulphur by dift illation. 



If thefe pyrites be fufed with a portion of potafh, the excefs Analyfis of the 

 of fulphur unites to this alkali, and the fulphuret of iron is re- compound py- 

 duced to the minimum. The aqueous fulphuric acid may then 

 be ufed to analyfe them. It diffolves all the fulphuret of iron 

 without affecting that of copper, which in that cafe prefents 

 itfelf with a deep blue colour, which is one of its characters. 

 By this means we may obtain the proportion of the two ful- 

 phurets which compote this kind of mineral. But when we 

 know the quantity of copper contained in a copper pyrites, 

 we always know that of the fulphuret of the metal, becaufe 

 in nature, as well as in art, copper never takes up more or lefs Copper in na^ 

 than 28 grains of fulphur per quintal. ture and a!lb b y 



If we with to afcertain the quantity of fulphuret in a cop- a &i y z % p e r 

 per pyrites, its nitric folution muft be precipitated by fulphu- cent « of fulphur. 

 rated hidrogen, and the precipitate ignited in a retort. The 

 product always reprefents the real quantity of fulphuret ori- 

 ginally combined in the mineral. 



Native Sulphuret of Manganefe. 



This fulphuret has not been noticed by mineralogifts as far Native fulphuret 

 as I know. I difcovered it fome time ago in certain fpeci- of man S anele - 

 mens of gold-ore from Nagyag. 



The gangue of the piece which afforded this fulphuret is a Hiftory and de- 

 carbonate of manganefe mixed with quartz, like that of the fcri P tio «- 

 fulphuret of Tellurium. It does not prefent metallic cryftals 

 of this metal, but a multitude of points, which under the mag- 

 nifier appear to be an affemblage of pyritous parts. This Treatment, 

 mineral treated with the aqueous fulphuric acid, affords a 



Vojl. I.— April, 1802. T very 



