48 APPENDIX. 



M. Damoiir suggests, in relation to the statements of M. Pavre 

 (referred to above), tliat 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 noAV 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, garnet, 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 matris 

 of diamond in Brazil, which he calls Itacolumite sandstone (a 

 secondary red sandstone), which overlies the crystalline beds, 

 and once had an enormous development ; to its denudation he 

 attributes 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 Geoloqie (ii, 

 379-383). 



In the province of Matto Grosso, at the water-parting of the 

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

 latitude, and at an elevation of some 1,200 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 Geraes, 

 between 16° and 26° S. latitude, and even comes down to the coast 

 at San Joao do Barro, where, in 1850, a chance washing of the 

 underlying schist disclosed the presence of many diamonds. The 

 deposit is not confined to the beds of rivers or ravines, but covers 

 the slopes and tops of the hills. This deposit ceases exactly at 

 the boundary of the bituminous beds of the coal measures of St. 

 Catherine. 



Is this, then, I would ask, any indication of the origin of 

 diamond in carboniferous rocks ? If so, ought not those rocks 

 to contain diamond ? 



In the north part of Minas Geraes, Jurassic calcareous forma- 

 tions cover the red sandstone, and these are in turn subordinate 

 to gypseous marls and rock salt. Yet, in the ravines, cut down 

 to the sandstone, thi'ough the overlying beds, diamonds are 

 found, i.e.^ above the Cai-boniferous formation. 



Moreover, in 1839, diamonds were discovered in the Psammite 

 of Serro de Santo- Antonio de Grammagoa imbedded in the rock, 

 whereas in the preceding Itacolumite sandstone they occur 

 between the plates of mica, just as garnets occur in mica-schist. 

 The edges of these are rounded, Avhilst in the Psammite the 

 angles are uninjured, proving that the transmutation of the 



