THE BINGEEA DIAMOND FIELD. 101 



Then too, iu Africa, they are found in a di-ift, and usually with- 

 in a few feet of the surface, from 3 to 9 feet, and rarely down so 

 far as 30 feet. 



Here, again, one of the main features of the district is the 

 presence of sandstone, either of Upper Silurian or Devonian 

 age ; trap is also present, and a conglomerate or breccia contain- 

 ing boulders of granite, gneiss, mica schist, porphyry, sandstone, 

 jasper, slate, agate, &c. 



In conclusion, we are still as much in the dark respecting the 

 origin of the diamond or even its true matrix, for no good proof 

 has yet been oifered on this question, as we have seen in nearly 

 all cases it occurs in an ancient river drift, and is usually associ- 

 ated with sandstones, conglomerates, and trap rocks ; neither do we 

 know the matrix of the sapphire, zircon, &c., which are usually 

 much rolled, as if they had been borne a great distance. The 

 sapphires from Bingera seem to have undergone but little altera- 

 tion, and consequently have not travelled far, so that perhaps 

 we may soon light upon their source and that of the diamonds 

 simultaneously. Bingera certainly seems the most hopeful locality 

 to elucidate this point of any at present known. 



Before closing this paper, I must express my obligations to 

 Messrs. Westcott and M' Caw, and to Mr. Dougherty of the Gwydir 

 Diamond Co., for their great assistance in procuring and sending 

 me suites of specimens illustrating the various rocks and minerals 

 of the diamond workings, and wish them success in their endeavours 

 to open up this industry, which I hope will prove to be a new 

 source of wealth to New South Wales. And this result appears 

 to be highly probable, since the whole of the above-mentioned 

 valuable finds have been made by the exertions of but a few, 

 perhaps not more than five or six workers. 



