Mode in which Gold occurs in Quartz.

Cromwell Argus, Volume III, Issue 142, 30 July 1872, Page 7

Mode in which Gold occurs in Quartz.

Mr John Yard contributes to the Sydney Mail the following information respecting the geological formations in which gold is likely to be found, —as the result of ten years’ practical experience in mining :

Gold reefs run into the earth in small crevices, and are thrown up through the surface of the earth’s crust where the volcanic eruption has been of sufficient heat. The reefs will be found to be more numerous on the surface in places where the burning of the earth has been most severe. Gold reefs have not been known to run out altogether in any country ; and where the deepest mines have been abandoned, it is not because the gold has been exhausted, but because of the difficulty of dealing with the water which has accumulated in the mines. Granite has been connected with all the superior minerals ; and granite formations rise to the surface of the earth in many parts of the colony. When they appear in the golden tracks, the gold is very thinly distributed. The reefs in those formations are of a very poor description, and in nearly all instances the alluvial workings are very shallow. When they go to any depth they have always to contend with a heavy drift and a large amount of water, and the gold is very patchy. Gold reefs in slate formations are the most productive kind, and it is here that the heaviest deposits are to be found, the gold being very coarse in the alluvial and likewise in the reef. The veins are of a good thickness, and their quartz jointy and soft. Their casements are of a soft description, with hard burnt streaks running through them, and loose gold is often to be got in the casements. Gold reefs which run through layers of basalt are of a thin description, and vary to a great extent until they come into slate casements, and the underlay is likely to fall slightly, but very slightly, to the west. Gold found in such reefs is very heavy, but extraordinarily patchy. Basalt is often taken for solid slate ; but that is a mistake. Slate in its hardest condition is very jointy and brittle, with no great space between the joints. The colour of gold-bearing quartz varies very much. The richest gold has been found in the blue quartz, and it is considered by all miners of experience the best and most productive of gold. It is found with gold in most basalt formations. Quartz of a dirty white colour, having red streaks running through it, is more regularly distributed with gold. Its reefs are more plentiful and lasting, and its gold is of a liner description, having coarse patches in places. It is generally a good small-paying quartz. The railky-looking quartz always contains very fine gold : but reefs of this sort are a very poor “spec.” in which to invest. When gold is found in them, it is in granite casements. Such quartz is generally honeycombed, and full of small crystals. It is to be met with more plentifully than quartz of any other colour, and has thrown out the gold which it contained into the alluvial tracks in which it is fi mud in Australia. Leaders or small veins running into the main reef follow from the surface of the earth to which they belong, and if they go deep, they connect with other leaders. If the leader traced from the surface is found to contain gold, it will be very narrow if rich, and in casements. The main reef to which it belongs will be of great depth. The rich veins will lie to the east, and poor ones will come into them almost perpendicularly. Where this takes place the leaders are numerous, and the main reefs are a great distance away. If the gold be very coarse in the leaders, the main reef will be very patchy, and probably no good ; but if rich with fine gold, then the main reef to which the leaders belong will be likely to be rich and regular. The term “ blow” is applied to a reef which has been vomited on the surface of the earth ; and blows will be seen on all goldfields in different places, but generally on the sides of hills and in mountainous country. They will be more numerous when the gold is of a coarse description. They are composed of large fragments of quartz lying on the surface, with strong indications of fire ; and the soil of the hills’ neighbourhood will be red. Gold found in the quartz of the blow is, in all instances, an indication that the reef will be likely to turn out well; the richer the blow the better. When the reef is found to contain good stone not far from the blow, then the prospect is good. Nos. 1, 2, and 3 north of the blow are considered in all instances a very good investment. Nos. 1, 2, and 3 south are in nearly all instances a fair prospect, with a moderate chance of something better. Outside those numbers on the blow, the ground is seldom worth anything. The reefs are hard to trace, and deep to sink for, because the reef catches its greatest dip into the earth.