MINING IN CALIFORNIA AND NEVADA. 45
of
our colonial mining experts, who will find me always in readiness to
explain or furnish further details of anything that could not be
described without the original diagrams. In describing the various
matters connected with CaTifornian mining, embracing the machinery
used for the manipulation of quartziferous gold ores, it should also be
understood that the delegate could not do more than describe them,
the practical working in detail of both, though grasped during his
inspections, can only be initiated and carried out by him when and
wherever required.
(d.) SAMPLING AND ASSAYING OF ORES.
In
California and Nevada the ores are subjected to periodical tests to
check, as much as possible, any loss that may arise from the use of
defective machinery, unsuitable manipulation, and carelessness by the
employes during reduction. In San Francisco there are establishments
which are recognised by the miners as dealing exclusively with all
kinds of ores, which may be shipped to them by sea or delivered by
rail. Of these ores, average samples are obtained by these firms for
the assayers employed by either the miners (vendors) or the purchaser
(metallurgists), and, as soon as the assays have been made, the bulk of
the ore stored by the " samples," is sold by tender, private
agreement, or sometimes by auction. This, of course, applies only to
such mines located in distant districts, which are, moreover,
inaccessible for the transport of heavy machinery, though frequently
mine owners dispose of concentrated ores from mines well equipped with
the best modern appliances.
The
ore as emptied from the bags (each 200 lbs.) is formed into a conical
heap upon solid granite floors; these heaps are then spread out and
divided into four parts by cutting two passages across the heap. The
inner portions of these passages are scraped into the gangways, and
this ore is thrown into the centre of the pile, which is then
thoroughly mixed, and about 25 lbs. are taken for the next operations
following in due course until about one pound of ore is left, which is
thereupon crushed upon a cast-iron table with raised sides by means of
a Cornish " bucking " hammer, and when fine enough to pass
through a screen with 3,600 meshes to the square inch, cones are again
formed; these are flattened out with a spatula when the final selection
is made as follows:—A concentric line a {see diagram), or furrow, should be
