DIAMOND: OCCURRENCE IN AUSTRALIA 223 



and it was in the gold-washings that the first discovery of diamonds was made. The 

 diamantiferoLis gravels and sands of these ancient river deposits, which are alwajs 

 above, and often far above, the present water-courses, are very frequently overlain by 

 a sheet of compact basalt, which must be penetrated before the diamond and gold- 

 bearing stratum can be reached. Re-deposited masses of material, containing both gold 

 and diamonds, often lie on the basalt, having been washed down from the upper part of 

 the valleys. 



The first discovery of diamonds in Australia was made in this State in 1851 ; the stones 

 were found in Reedy Creek, a tributary of the Macquarie river, sixteen miles from Bathurst ; 

 a few were found in the same district in 1852, in Calabash Creek. In 1859 a few stones, 

 having the form of triakis-octahedra, were found in the Macquarie river, near Suttor's Bar, 

 and at Burrandong ; in the same year a hexakis-octahedron, weighing 5^ carats, was found 

 in Pyramul Creek. These places are all situated in the same district, and at none of them 

 were more than a few stones found. 



In 1867, however, diamonds in greater number were met with near Warburton, or Two 

 Mile Flat, on the Cudgegong river, nineteen miles north-west of Mudgee ; and in 1869 the 

 systematic working of an area of about 500 acres in this district was commenced. The 

 working, which was not very profitable, was carried on at Rocky Ridge, Jordan's Hill, Horse 

 Shoe Bend, and Hissalt Hill, as well as at the places already mentioned. The ancient river- 

 deposits in which the diamonds are found lie under a capping of columnar basalt, and occur 

 at isolated spots along the course of the Cudgegong river, more or less distant from the 

 present river course, and at heights up to 40 feet above the present high-water level. 

 They rest on the eroded edges of perpendicular sedimentary strata, which are interbedded 

 with compact greenstones, and probably belong to the period of Upper Silurian deposits. 

 The diamond-bearing debris consists of coarse sand and mud intermingled with pebbles of 

 quartzite, sandstone, clay-slates, and quartz-slates, accompanied by waterworri grains and 

 crystals of quartz, jasper, agate, silicified wood (this in large amount), and oth^r siliceous 

 minerals, also cassiterite (the " wood-tin " variety), topaz, common corundum (sometimes of 

 a lavender-blue colour), sapphire, ruby, a peculiar variety of corundum called barklyite, 

 zircon, garnet, ruby-spinel, brookite, magnetite, ilmenite, tourmaline, magnesite, nodules of 

 limonite, grains of iridosmine, and, of special importance, gold. The' quartz pebbles are 

 frequently encrusted with oxides of iron and manganese. The whole mass of diamantiferous 

 debris is in some places loose and incoherent, and in others bound together to form a solid 

 conglomerate, the cementing material being a green, white, or grey siliceous substance, or a 

 brown or black ferruginous or manganiferous substance. The deposit in places attains a 

 thickness of 70 feet ; the diamonds, which are of small size, are scattered through it so 

 sparingly and irregularly that the working of it cannot be profitably prolonged for any length 

 of time. 



In spite of the poor character of the deposit, 2500 stones were found during the first 

 five months of work. All were small, the largest being the octahedron of 5| carats men- 

 tioned above, which, when cut, formed a beautiful colourless brilliant, weighing S^V carats. 

 The stones average in weight about ^ carat, and vary considerably in colour, passing from 

 perfectly water-clear through various shades of yellow, pale green, and brown to almost 

 black ; a twinned octahedron of a beautiful dark-green colour was once found. The 

 commonest crystalline forms are the octahedron, which occurs both as simple and twinned 

 crystals, the rhombic dodecahedron, triakis-octahedron, and hexakis-octahedron ; one crystal 

 with the form of a deltoid dodecahedron has been found. The crystals are, as a rule, much 

 water-worn ; when this is the case their surfaces are sometimes smooth and bright, at other 



