1822.] Variegated Copper Ore. 83 



ages are, however, attainable parallel to all the planes P, though 

 not sufficiently brilliant for the use of the reflective goniometer ; 

 but determinate enough to satisfy me that the primary crystal is 

 the regular octohedron. 



" The primary octohedron, besides the modifying planes by 

 vv^hich it so nearly passes into the cube, is also subject to another 

 modification, causing it sometimes to assume a form which 

 might be mistaken for a rhomboid ; but its planes are not suffi- 

 ciently defined on any of the crystals in my possession to allow 

 of measurement or determination. 



" The preceding measurements and remarks it is presumed 

 will suffice to show that this substance is not derived from copper 

 pyrites, and that its crystalline forms are not in any degree allied 

 to those of that substance, which does not occur in the form of 

 the regular tetrahedron or octohedron. 



'* It may not be amiss to add, that the buntkupfererz is some- 

 times found in the mines of Cornv/all apparently in the form of 

 the six-sided prism, frequently tabular, or in crystals which 

 approach in form to a double six-sided pyramid with triangular 

 planes, and which are allied to the six-sided prism ; the use of 

 the knife, however, will always, as far as my observation goes, 

 evince that it is merely a coating of the buntkupfererz, on crys- 

 tals of the vitreous copper." 



Klaproth has given two analyses of this ore, one specimen 

 being from Hitterdahl, in Norway, and the other from Rudel- 

 stadt, in Silesia : the results are thus stated : 



From Hitterdahl. From Rudelstadt. 



Sulphur 19-0 19 



Copper 69-5 58 



Iron 7-5 18 



Oxygen 4*0 .....* 5 



100-0 100 



It is difficult to conceive that this mineral varies so much 

 in its composition as that the copper in on«i specimen should 

 exceed that of the other in the proportion of 69*5 to 58, or that, 

 as also stated by Klaproth, the quantity of iron in one should be 

 more than twice as great as that in the other specimen ; if 

 thev had been crystallized, this difference might be supposed 

 to have arisen from a cause already mentioned ; namely, that 

 other copper ores are sometimes covered with this. 



In order to form some idea of the probable constitution of the 

 variegated copper ore from both these analyses, I shall state 

 what are, I believe, almost universally, or with Uttle variation, 

 allowed to be composition of sulphuret of copper, sulphuret attd 

 persulphuret of iron. 



g2 



