GEOLOGY AND MINEEALOGY. 187 



In this light, the following Table, drawn up chiefly from the researches of M. 

 Hcgard, of the Geological Society of France, will be found to exhibit some in- 

 teresting relations : 



Approximate amounts of inorganic matter in animal bodies which oecur more 

 frequently in the fossil state : 



Inorganic matter, 99 or more per cent : — Shells of Ostreae and of some other 

 acephalous mollusks. 



Inorganic matter, 95 to 98 per cent: — Most corals ; shells of most bivalves and 

 gasteropods. 



Inorganic matter, 90 to 95 per cent: — Shells of ordinary cephalopods. 



Inorganic matter, 60 to 70 per cent: — Teeth of mammals, reptiles, and many 

 fishes. 



Inorganic matter, 50 to 66 per cent : — Bones of mammals, birds, and reptiles ; 

 scales of fishes; carapace, &c, of chelonians?; shells of crustaceans. 



Inorganic matter, 40 to 50 per cent: — Elytra of certain insects (?). 



Inorganic matter tender 5 or 6 per cent: — Scales of reptiles; cartilage and hair 

 of mammals ; feathers of birds, &c. 



A glance at this table will explain the cause, (as pointed out by M. D'Orbigny,*) 

 of the rare occurrence of reptilian scales in the fossil state, whilst the scales of 

 fishes are so abundant. — E. J. C. 



PURPLE COPPER PYRITES. 



Purple Copper Ore — the Buntkupfererz of the Germans; Erubescite: Dana — 

 in pseudomorphs, after chalkopyrite, the common yellow pyrites, does not appear to 

 have been hitborto recognised. Pseudomorphs of this kind occur, however, and 

 seemingly in abundance, amongst the copper ores of Lake Huron. Their usual 

 form is that of the ordinary dimetric tetrahedron, belonging to chalkopyrite. When 

 broken across, a nucleus of this latter mineral is frequently seen within them. 

 The purple ore may be readily distinguished from Urnished or variegated specimens 

 of chalkopyrite. by its higher specific gravity. A portion of a crystal (G=4.77) 

 contained 63.19 per cent, of copper ; and two other specimens (in which, however, 

 the copper was alone determined, and by a less satisfactory process,) shewed a still 

 larger amount. In the first determination, the copper was separated from the iron 

 by sulphuretted hydrogen, and weighed in the usual way as oxid<\ An analysis of 

 16.52 grs., thu3 furnished — sulphur, 3.97; copper, 10.44 ; iron, 1.96; or, in per- 

 centage values — sulphur, 24.03 ; copper, 63.19 ; iron, 11.8'S. The composition of 

 purple copper is known to vary greatly, and it-; true formula is yet unsettled. Two 

 formula? have been proposed for it. The one adopted by Berzelius, 2Cu«S+ 

 FeS., requires S. 23.7, Cu. 62.5, Fe. 13 8. The other, assumed by Rammelsberg, 

 3Cu2S+Fe2S : * , gives S. 28.1., Cu. 55.5., Fe. 16.4.; but in the analyses 

 hitherto published, the copper is always in excess of 55.5, and generally over 60. f 

 At the same time, it is difficult not to admit that a higher degree of sulphurization 

 than RSmust be present in the mineral. Rammelsberg attributes the excess in ques- 

 tion to an admixture with copper glance, CuSS: a compound which also occurs 

 amongst the Lake Huron ores, and which i? known furthermore to occur occasionally 

 in other localities as a product of alteration from copper pyrites. — e. j. chapman. 



* "Cours de Pal£ontologie et de Gtologie Stratigrapbiqnes." 



\ See the results of nineteen separate analyses in the 4th edition of Dana's 

 " Mineralogy,'* II., 38. 



