AND MUDGEE DIAMOND-FIELDS. 491 



author describes the process adopted, which he thinks must cause 

 the loss of many diamouds. He also mentions the average number of 

 diamonds per load of drift obtained in certain workings. 



The Drift. — The characters of the diamantiferous drift of the 

 Bingera diamond-field are as follows: — On the surface there are 

 boulders and large pebbles of various kinds, principally siliceous, and 

 elongated pebbles of a very fissile argillaceous sandstone, the 

 smaller of which are termed " finger-stones " by the miners, and re- 

 garded as a favourable sign. Blocks of very compact conglomerate 

 occur among the other rolled stones ; the smaller pebbles in this are 

 generally subangular. 



The drift itself is largely composed of clay and sand. The clay 

 shows a brecciated structure, as if recently derived from a commi- 

 nuted shale ; and parts of it, when freshly dug out, are of a bright 

 green colour, probably due to ferrous silicate, as it becomes pale 

 brown on exposure. Large blocks of the bed-rock are found in the 

 drift. Minute crystals of selenite occur in the clay. 



The larger pebbles include rolled white quartz (apparently vein- 

 quartz), red, green, brown, black, yellow, and veined jasper, a little 

 cacholong, black flinty slate, concretions of limonite, generally sphe- 

 rical (occasionally imbedded in rolled masses of magnetite, within 

 which the nodules seem to have formed by segregation of iron 

 oxide), botryoidal carbonate of iron, rolled masses of very soft shale, 

 and a little petrified wood. The pebbles are not glazed as in the 

 Cudgegong deposits. 



The residue left after the puddling process consists of sand and 

 small pebbles, and is known as " gem sand." It is from this that 

 the diamonds are picked out. Associated with the diamonds in it 

 are the following minerals : — 



1. Topaz, generally rolled and water-worn, colourless and trans- 

 parent, sometimes greenish. 2. Corundum, usually in small angular 

 blue and green fragments. 3. Quartz, as rolled pebbles and worn 

 crystals, also jasper and small black pebbles of flinty slate, the 

 presence of which is regarded as a good sign by the miners. Small 

 jaspery pebbles, usually measuring about ^ in. by § in., showing 

 light mottled tints of drab, yellow, brown, pink, &c, and pretty 

 highly polished, are known as " morlops " by the miners, and re- 

 garded as furnishing favourable indications. 4. Tourmaline, in 

 rolled black crystals about g inch long. 5. Spinel, of a dull red or 

 pinkish colour, often much broken. 6. Zircon, in small rolled 

 fragments and crystals, colourless, red or brown. 7. "Wood-tin, 

 rare, in small rolled pieces. 8. Ilmenite, not common. 9. Brook - 

 ite, rare, in flat, rolled, translucent plates. 10. Magnetic iron-sand, 

 in minute brown grains, sometimes showing octahedral form under 

 the microscope, strongly magnetic. 11. Garnet, in small, ill-formed 

 reddish-brown crystals, not very common. 12. Gold, rather scarce, 

 usually in very thin spangles, generally attached to the magnetite. 

 13. Osmiridium, rare, in small, flat, heavy plates. 



The diamonds are generally small, and the crystals not particu- 

 larly well developed ; the faces are usually much rounded. They 



