SULPHTJRET Of LEAD, COPPER, AND ANTIMONY. 3$ 



variety from Andreasberg in the Hartz, having afforded him 

 034 of lead, occasioned its removal from the copper to the 

 lead ores ; among which many German mineralogists conti- 

 nue to class it, expressing doubts however, respecting the 

 nature of its real component parts. Nothing is more variable 

 than the analyses, that have been made of different gray sul- 

 phuretted copper ores, taken even among those that are 

 crystallized ; and it is absolutely impossible to found upori 

 these any determinate classification of the species and varie- 

 ties of this ore, unless we previously establish certain fixed 

 points, to which we may refer them. 



In tbis state of things I conceive we ought to consider the Division of t 

 sulphuretted copper ores in two different points of view ; cop P pe"o"s 

 the first regarding those that admit a determinate form ; the 

 second, such as have not hitherto appeared to admit any, as 

 the weissgueltigertz and graugueltigertz of the Germans, &c. 



Among such of these ores as take a determinate form we Distinction o» 

 ought, I think, to consider as belonging to one species the s P ecies - 

 those, that constantly take the same primitive form, or some 

 one of its modifications. At the head of this we should simple sulph > 

 place, first, the simple suiphuret of copper, composed of ret of «°pper. 

 0*81 copper, and 0*19 sulphur. Its primitive form is a 

 right hexaedral prism, the terminal faces of which are 

 regular hexagons *, and the specific gravity of which is 



5.643. 



* My intention is soon to lay before the 'Royal Society a more 

 complete detail, relating directly to these copper ores, in which the 

 form and dimensions of these crystals will be established. 



Addition. When I entered into this engagement, I was not 

 aware of the fate, that awaited the paper in which it was inserted. 



The height of the regular hexaedral prism, forming the primi- Primitive crys 

 tive crystal of the simple suiphuret of copper, is to the apothema§ taf of sulphur* 

 of the regular hexagon, that serves as its base, in the ratio of 2 to 3, 

 a ratio determined from three different substitutions for the edges 

 of the same hexagons, the planes of which make with the terminal 

 faces for the first an angle of 146° 19', forthesecond 13S° 22', and 

 for the third 1 16° 32'. Frequently all the planes owing to these three 

 modifications terminate the same prism. Often too they reach each 

 others limits, and then giveriseto as many hexaedral pyramids, eil her 



terminating 



§ The apothema is u perpendicular line let fall from the centre of 

 the circle in which the hexagon is inscribed, and bisecting any one 

 qf its sides. 



