'i4!6 Mechanical Asso.y of Quartz. 



piece of india-rubber hose pipe, I employed a sieve of 

 brass wire of fine mesli (say about nine hundred to 

 the square incli), and after all the sample had passed 

 through the sieve, I ground the powder still finer in 

 a shallow cast iron mortar of about 11 inches diameter 

 and 5 inches deep : this mortar was cast from the 

 pattern of a Berlin porcelain druggists' mixing mortar, and 

 has proved a most useful tool. I then submitted a weighed 

 quantity of the verj" finely ground sample to careful washing 

 in a porcelain dish, and eventually obtained a residue con- 

 sisting almost entirely of the metallic sulphides of the ore. 

 These, small in bulk in proportion to that of the original 

 quartz sample, were now transferred to a large agate mortar, 

 again ground and washed alternately, until at last a small 

 gray residue showing no gold was all that remained. This 

 gray residue consisted almost entirelj^ of particles of cast and 

 wrought iron abraded during the preceding operations. They 

 may be easily separated. A darning needle or a steel pen is 

 magnetised by drawing it once or twice, always in the same 

 direction, over the surface of an ordinar}^ horse-shoe magnet, 

 and to the little steel magnet thus obtained, the particles of 

 iron will attach themselves, and may be freed from any 

 entangled particles of gold by drawing them backwards and 

 forwards through the water with which the agate mortar is 

 filled. I may mention that the agate mortar is pre-eminently 

 suitable for this final work ; the smallest particle of gold 

 can be seen against the dull surface of the agate ; the 

 hardest materials can be ground impalpably in the little 

 vessel and it serves the double capacity of mortar and wash- 

 bowl ; we can wash and grind alternately to the close of the 

 ■operation. 



When the gold is finally separated in spangles or flattened 

 particles in the agate mortar, accessory chemical means for 

 refining and collecting the precious metal into a globule may 

 be employed. The gold residue may be wrapped in a 

 morsel of sheet-lead, and cupelled before the blowpipe ; and 

 from the diameter of the resulting minute spherical bead of 

 fused gold thus obtained, its weight may be easily computed. 

 Such operations are familiar to the chemist in the labora- 

 tory, but, I fear, would in. most cases prove inapplicable in 

 the hands of the miner in the field. I refrain, therefore, 

 from troubling 3'ou with further details of a treatment which 

 must be regarded as extrinsic to the purely mechanical 

 assay, especially as the fullest particulars of all operations of 



