THE BINGEEA DIAMOND FIELD. 93 



The rocks are generally devoid of mica. For the most part 

 the Older Pleiocene diamond-bearing drift is coarse and loose, 

 but parts are cemented, together into a compact conglomerate by 

 a "SA'hite cement of a silicious nature, sometimes rendered green 

 by admixture with silicate of iron ; in other cases oxides of iron 

 and manganese have been the agglutinating agents. Diamonds 

 were proved to exist in this solid portion by a special experiment 

 of Mr. Taylor's. 



The drift is chiefly made up of boulders and pebbles of quartz, 

 jasper, agate, quartzite, flinty slate, shale, sandstone, with abun- 

 dance of coarse sand, and. more or less clay. 



The quartz pebbles are white, like vein quartz, but often 

 encrusted with films of iron or mauganese oxides. 



Many of the boulders and pebbles are remarkable for a most 

 peculiar brilliant silicious polish, which is evidently not due to 

 friction, since the cavities are equally well polished. Silicified 

 wood is common, and coal has been found iu the river higher up : 

 also carboniferous fossils, such as Favorites Gothlandicaand others. 



Amongst the minerals associated with the diamond are the 

 following. This list, we shall see, is almost identical with that 

 furnished by Bingera : — 



1. Black vesicular pleonast. This mineral has not yet been 



found at Bingera. 



2. Topaz. 



3. Quartz. 



4. Corundum. 



a. Sapphire. 



h. Adamantine spar. 



c. Barklyite. 



cl. A bluish white variety, characteristic of Mudgee. 



e. Euby. 



f. Rolled corundum, dirty white and pink. 



5. Zircon. 



6. Tourmaline. 



7. Black titaniferous sand. 



8. Blaclf magnetic ironsand. 



9. Brookite. 



10. Woodtiu, rare. 



11. G-arnets. 



12. Iron, from tools. 

 18. Gold. 



14. The Diamond. 



The largest found was 5|- carats :=: roughly 16"2 grains. The 

 average sp. gr. was 3'44 ; and the average weight 0'23 carat, 

 or nearly one carat grain each. The carat contains 4 carat grains, 

 which are equal to 3'16 grains troy. 



