appendix, 47 



Diamonds est Brazil. 



Brazil seems naturally to claim our first attention. It has 

 been found that in a certain Brazilian rock called Itacolumite, 

 diamonds have been found in situ, and therefore all diamonds 

 are assumed to have been derived in a similar way, wherever a 

 rock imagined to be Itacolumite exists. 



In 1846, Professor Shepherd, of South Carolina (A. S. J. II., 

 253), announced the extensive development of the rock in that 

 State, and he gives a figure and description of a diamond from 

 gold washings in that formation. 



In Brazil, however, they occur in great numbers in the lower 

 Itacolumite beds. 



According to Humboldt this rock belongs to the very oldest 

 sedimentary deposits. 



So far as my own observation has gone this rock does not occur 

 in New South Wales, and even in Brazil, as I will show, diamonds 

 are not confined to it. My friend Mr. Ulrich, late of the Victo- 

 rian Survey, says the same of the sister Colony, and assures me 

 he had very good opportunities of satisfying himself by examin- 

 ing the Brazilian specimens at the last International Exhibition at 

 Paris. Humboldt (JEssai Geognostiq^ue, Paris, 1820, jy. 89,) 

 includes Itacolumite in the quartz rock series parallel with his 

 primitive clay slate. 



Yon Cotta places it among the crystalline schists, and 

 describes it as a fine-grained micaceous talcose or chloritic schist, 

 somethnes flexible, holding occasional quartz pebbles with magnetic 

 iron and gold, as well as diamond. According to Eschwege, it 

 passes into Itahirite, which belongs to the lied Haematitic group. 

 Other writers include it with " micha schist," " quartz of the 

 mica slate," and " elastic sandstone." Heusser and Claraz con- 

 sider it a " granular quartz," sometimes bearing quartz-veins with 

 pyrophillite lime ; others consider it an iron schist. 



Eschwege says it attains in Brazil a thickness of many thousand 

 feet, ranging for hundreds of miles. 



The North 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. 8. G. de France, xiii, 2Dd 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 thirty-two mineral species, — among them very 

 minute rhombohedral dodecahedrons of garnet of a topaz yellow 

 colour ; a similar occurrence to that of Two-mile Plat, noticed 

 by Mr. Norman Taylor, where Irown garnets of the same form 

 occur. 



