Mechanical Assay of Quartz. 14] 



we deal at most with pounds weight, and not with hundreds 

 of tons, and the expenditure of time devoted to the work is 

 a far more serious item than that incurred for chemicals 

 instruments and fuel. I wish to convey a discriminative 

 view of this point ; I wish j^ou to understand that all the 

 resources of the laboratory are available for the assay ; that 

 with the small quantities operated on in such trials, means 

 are available, which would prove far too expensive for use 

 on the large scale : but I must also add, that the quartz 

 assay, which to be valuable must be accurate and wholly 

 reliable, is not so accessible as could be desired. It is a 

 valuable key to the operations of quartz mining and crush- 

 ing, but yet is used only to a limited extent. In a large 

 proportion of cases the quartz assay is beyond reach ; the 

 prospector in the ranges is remote from the metallurgical 

 laboratory, and in other cases the cost of the assay is a 

 hindrance ; a certain cash outlay for what may be considered 

 (justly or otherwise, according to circumstances), a possible 

 and perhaps remote advantage. 



Let me endeavour to convey to those members who have 

 not a practical acquaintance with the subject, a general 

 notion of the way in which a quartz assay is usually 

 conducted. I will endeavour to do so in the fewest words. 

 I will suppose a few stones which collectively are regarded 

 as fairly representing the reef Of course the fairness of 

 this representation involves the whole question at issue, and 

 a good deal might be said on this point, but I will not 

 digress to take up your time with that matter. I will 

 suppose that no gold is discoverable by mere inspection in 

 the newly found reef ; that none is seen in the sample of 

 stone selected ; the stones are regarded as a fair sample, but 

 that is; a mere matter of probability and judgment, and it is 

 deemed advisable to find out, before proceeding further, what 

 gold this sample contains. I will suppose that the specimens 

 are quartz for the most part, with admixture of clay slate, 

 oxides of iron and brassy iron p^^rites ; quite a common 

 combination. 



The gross weight of this sample is taken, it is then 

 pidverized finely and passed through a wire sieve of fine 

 mesh. Of coiirse, as gold is malleable and as the quartz, 

 and its other accompaniments are brittle, any coarse gold 

 existing in the sample, and separated by pounding it, may 

 remain on the sieve, and should such malce its appearance, 

 its weight is referred to the otoss wei^'ht of the stone 



