Sampling

A discussion of sampling, although fully treated elsewhere, cannot logically be omitted; inasmuch as proper sampling is often neglected, the subject will bear repetition.

Sampling is expensive work if properly carried out, and no other kind of sampling is of any value.

The ideal sample is a uniform groove, or channel, across the full width of the ore, and no more; how closely this may be approached in practice will depend upon the material sampled and upon the time and care given to the work.

The Equipment for Sampling.—A hammer and moil are preferable to any other tools in cutting samples; a prospector's pick will do good work in soft, uniform ground, but in harder material, even if the point and hammer-end are alternately used, is likely to have a selective effect, and samples taken with a pick are not above suspicion.

To catch the sample a cloth is best, spread out so as to catch all chips. If the ground is loose and masses are likely to fall, the sample is best caught in a box, which is also used where fine, rich material is likely to sift out of cracks and vugs and so find its way into the sample.

To break down samples a crusher is convenient, but two large, tough stones of barren rock such as may be found in any creek bed, one to lay the ore upon and the other to pound with, yield the maximum result for coarse breaking; unless the ore is very hard, the abrasion of the stones is negligible.

To cut down samples, rolling and quartering on flexible oilcloth is a good method, but where many samples are to be taken, a Jones sampler with four pans, or a riffle, is quicker and more certain to do accurate work.

A simple apparatus to permit the cutting of samples in an untimbered shaft has been used by the writer with great saving of time and expense over erecting platforms. This consists of a short seat, about 14 in. long by 6 in. wide, to which is rigidly fastened a pole in length about one and one-half times the width of the shaft to be sampled. This seat is fastened to the end of the windlass rope, and, straddling the rope, the sampler is lowered to the point where a sample is to be taken, meanwhile holding the pole parallel to the rope so as to permit the descent. Arriving at the point where the sample is to be taken, the pole is allowed to fall against the opposite wall, the end of the pole catch ing in an inequality of the rock, the seat is hoisted a few inches, and the sampler, with feet braced against the face sampled, is held firmly and safely in position, with both hands free to work. The sample may be caught in a bag held between the feet, or a canvas receptacle may be rigged in front of the sampler, or the sample may be allowed to fall on a canvas spread over the bottom of the shaft, which should be protected from the impact of the falling ore by a few boards; the latter is usually not a safe method unless the men at the \-indlass are closely watched, as salting by them would be an easy matter.