Mechanical Assay of Quartz. 145 



tools and a little patience we can grind our sample until it 

 is almost impalpably fine. We must bear in mind that the 

 quartz, the arsenical pyrites, all the contained minerals, 

 excepting the gold, are brittle, and that the gold alone is 

 malleable, and this reminder should be kept in view in 

 considering the example to which I beg in the next place to 

 refer. 



I had visited a reef in the neighbourhood of Wellington, 

 New South Wales : a bold reef cropping out of the ground 

 like a string of mile or tombstones stretching across country. 

 The quartz contained strings and geodes of agate, as well as 

 copper carbonates, copper pyrites and other minerals, — a well 

 mineralized reef, in which, however, no gold was visible. 

 Feeble attempts had been made to work it, and after inquiry 

 I obtained from a person living close to the spot one small 

 specimen from this reef in which a viinute speck of gold 

 was visible by aid of the pocket lens : this gold particle 

 detached and fell out before my return with it to Melbourne. 

 Shortly after my return, I obtained a box of the stone of 

 this reef, and I carefully assayed it in the fire, with a result 

 equal to 15 dwts. of gold to the ton. I was surprised at 

 this relatively large yield from stone showing no gold, and 

 repeating the trial I again obtained exactly the same result 

 of 15 dwts. So close a coincidence in the results of these 

 assays would suggest that the gold was very uniformly 

 distributed in a very fine state of division throughout the 

 stone. I then took a sample of the stone, pulverized it very 

 finely, and treating it in a way which I will presently 

 describe, I obtained the result of numerous flattened particles 

 or spangles of gold, all visible with the naked eye, but so 

 minute as to be much better seen and identified under the 

 microscope. Here then was a practical illustration of what 

 I am about to advance, namely, that the auriferous nature 

 or otherwise of quartz may be readily ascertained by means 

 for the most part mechanical ; and in the instance just 

 adduced you will observe that we gain an insight into the 

 mode of occurrence of the precious metal, and consequently 

 as to the treatment which such a quartz would require in 

 the mill. 



My mode of procedure was simply this. I first pulverized 

 the sample in a very large cast iron mortar ; this mortar 

 has a very stout bottom, the pestle, which is of wrought 

 iron, is 4 feet long, weighs 13 lbs., and the upper part of this 

 pestle for preservation of the hands is covered with a short 



L 



