in the interior of Cupriferous Minerals. 13S 



. Aceording to the analysis by Mr Richard Phillips of a spe- 

 cimen of variegated copper from Ireland, this species is com- 

 posed of one atom of protosulphuret of iron, and four atoms 

 of sulphuret of copper, or Fe S^ + 4 Cu S. The three in- 

 gredients, copper, iron, and sulphur, are in the ratio of 62.67, 

 13.44, and 23.89- 



The composition of copper-pyrites, from the analyses of 

 Professor Henry Rose, might be considered as being essen- 

 tially one atom of protosulphuret of iron, and one atom of a 

 sulphuret of copper, which contains twice as much sulphur 

 as the native sulphuret, the latter forming the species of pris- 

 matic copper-glance. Professor Rose is of opinion, how- 

 ever, that the copper contained in the mineral is in com- 

 bination only with one atom of sulphur, as in other species, 

 and that the whole mixture should be considered as a com- 

 pound of one atom of protosulphuret of iron, one of persul- 

 phuret of iron, and two of the sulphuret of copper. The che- 

 mical formula is therefore Fe S^ -h Fe S* -f- 2 Cu S, and the 

 three ingredients, copper, iron, and sulphur, are in the ratio 

 of 34.80, 29.83, and 35.37. 



The changes, therefore, can be explained upon the suppo- 

 sition, that the copper contained in the original species has 

 been replaced by iron, in a smaller quantity, however, as every 

 particle of iron required twice the quantity of sulphur to be 

 converted into protosulphuret in the variegated copper, and 

 four times the quantity for that portion of it in the copper- 

 pyrites, which is in the state of persulphuret. The compound 

 of protosulphuret and persulphuret of iron, which, in the last 

 species, is joined to the sulphuret of copper, is one of those 

 forming the chemical constitution of magnetic pyrites. ^ 



When the sulphur is entirely driven off, and the copper 

 attracts so much oxygen as to be converted into the peroxide, 

 the substance of what is usually called black copper results. 

 During this process often some of the carbonate is likewise 

 formed. 



