Anniversary Address. 17 



Tlie I^ortla Carolina species lies between limestone and clay 

 slate. It is said that it occurs in Portugal, Spain, and on the 

 Ehine. But this is doubtful. On the whole, it may be held to 

 be a transmuted sedimentary rock — a friable quartz or sandstone. 



M. Damour (Bull. S. G. de France xiii., 2nd Ser., p. 543) 

 mentions the occurrence in Brazil of diamond bearing sand, near 

 Bahia, containing numerous minerals and ores, and states that the 

 diamonds often contain spangles of gold in their cavities. He 

 enumerates 32 mineral species, among them very minute rhombo. 

 hedral dodecahedrons of garnet of a topaz yellow colour ; a 

 similar occurrence to that of Two Mile FJat, noticed by Mr. 

 Norman Taylor, where Iroivn garnets of the same form occur. 



M. Damour suggests, in relation to the statements of M. Favre 

 (referred to above), that the occurrence of the same minerals 

 with diamond in different countries would throw some light on 

 the formation. I may add that this is the principal reason which 

 induces me now to enter so fully into this discussion. 



Mr. Taylor instances as many varieties as M. Damour ; but the 

 so-called gems in the list given by the latter are confined to 

 Quartz, Zircon, Grarnet, and Tourmaline ; Ruby, Sapphire, and 

 Corundum being absent, and Euclase having been since added. 

 The metals seem to predominate. 



There is according to M. Claussen, another solid matrix of 

 diamond in Brazil, which he calls Itacohimite sandstone ( a sec- 

 ondary red sandstone), which overlies the crystalline beds, and 

 once had an enormous development ; to its denudation he attri- 

 butes a considerable portion of the materials forming the mixed 

 erratic diamond-bearing deposits ; but in this he finds neither 

 gold nor platinum. M. d'Archiac gives a very clear abstract of 

 Claussen's remarks in his Progres de Oeologie (il., 379-383 ). 



In the province of Matto G-rosso, at the waterparting of the 

 basins of the Amazon and Parana Elvers, a little south of 14° S. 

 latitude, and at an elevation of some 1200 feet above the sea, is 

 the diamond field of the Sierra Diamantina. 



But the most important field in a geological, if not commercial 

 view, is that which, ranging at a distance full 900 miles S.E. of the 

 former, stretches through the province of Minas Q-eraes, between 

 16" and 26° S. latitude, and even comes down to the coast at San 



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