iSyi.] Mineralogy. 287 



Jersey.* In affecting a cubic instead of an octahedral form the specimens are 

 crystallographically unique, whilst they are notable chemically for the large 

 proportion of zinc which they contain — 40 per cent of zinc oxide, and 50 of 

 alumina being the main constituents. 



An analysis of the Stewart-county meteorite has been published by Mr. J. 

 Lawrence Smith. f The stone fell at about 11.30 a.m., on October 6th, 1869, 

 in Stewart Co., Georgia, U.S. ; and the details of observations relating to its 

 fall have been collected by Professor Willet. A single stone has been found 

 weighing 12^ ozs., and covered externally with a dull black coating. It 

 presents an irregular conical shape, has a specific gravity of 3*65, and contains 

 7 per cent of nickeliferous iron, 61 of magnetic pyrites, and 869 of bronzite, 

 olivine, albite or oligoclase, and chromic iron. 



It has been shown by Professor Church that many of the hyacinth-coloured 

 gems usually known to collectors and jewellers as jacinths or hyacinths are 

 nothing more than garnets of the variety termed essonite. Indeed, the true 

 red zircon, or hyacinth proper, is much rarer than has generally been imagined, 

 and hence it is interesting to learn from Professor Church;}; that certain rolled 

 pebbles lately brought to this country from Mudgee, in New South Wales, are 

 veritable hyacinths, and agree in their pyrognostic characters with the well- 

 known zircons of Expailly, in France. 



About three years ago attention was directed to the occurrence of gold on 

 the Cudgegong River, in New South Wales, and a great rush was accordingly 

 made to a locality known as the Two-mile Flat. It was not long, however, 

 before diamonds were detected by the gold-diggers ; and although the discovery 

 ' attracted at first but little notice, workings in quest of the precious gem were 

 eventually set on foot by the Australian Diamond Mining Company. A visit 

 to the washings on the Cudgegong, near Mudgee, has enabled Mr. Norman 

 Taylor and Professor A. M. Thomson, of Sydney, to prepare some interesting 

 notes on the occurrence of the diamond in this locality. 



The diamonds are distributed somewhat sparingly and irregularly through 

 certain outlying patches of an ancientriver-deposit, similar to what is known 

 in Victoria as the older Pliocene drifts. 



They are for the most part transparent and colourless, but many present a 

 pale straw tint ; whilst some have been found of green, brown, and even 

 black colours. One opaque black diamond has been recorded. The average 

 size of the stones is small, and the largest hitherto discovered weighs only 

 5I carats. Many of the diamonds are well crystallised, and it is notable that 

 their faces and edges have suffered little or no abrasion, whilst the accom- 

 panying minerals have been much water-worn. The most characteristic of 

 these mineral are a vesicular black pleonaste, or spinel ; brookite, or oxide 

 of titanium, mostly in flat reddish transparent plates; and a bluish-white 

 opaque corundum in six-sided slightly barrel-shaped prisms, with flat terminal 

 planes. In addition, however, to these minerals, which are especially character- 

 istic of the diamond-bearing deposits of the Cudgegong, there are found also 

 topazes, generally white, in water-worn fragments and sometimes in crystals ; 

 quartz in ordinary double-hexagonal pyramids, and in pebbles including 

 varieties of cornelian, jasper, and agate; sapphire — blue, green, yellow, or 

 parti-coloured ; ruby occurring" but sparingly,- and in small flat grains ; 

 Barklyite, or an opaque magenta-coloured corundum ; zircons in brown, red, 

 and colourless fragments, and also as a sand ; tourmaline in rolled black 

 prisms; black magnetic and titaniferous iron-sand; garnets; wood-tin; and 

 native gold. The authors enhance the value of their paper by publishing 

 analyses of the pleonaste and of two of the varieties of corundum which occur 

 in association with the Cudgegong diamonds. 



Those who are interested in the diamonds of South Africa, and the geolo- 

 gical conditions under which they are found, may consult with advantage an 



* Silliman's American Journal, Jan. 1871, p. 28. 



t Ibid, Nov., 1870, p. 339. 



$ Chemical News, Feb. 17, 1871, p. 78. 



