The gold prospecting activity may generate different types of samples and its size is important in order to have a good sample. The size of a sample should be limited to the least amount that will yield a true average of the exposure sampled. A few large samples are of little value as compared with many smaller samples, if the latter be well taken. As a bunch of rich gold ore is capable of salting the whole sample and any sample that is too large to be sealed in a sack and properly protected against salting is a source of danger. Some metallurgical tests are not satisfactory on any but very high-grade ores, as the clean-up will depend largely upon whether the plates are scraped clean or whether they are allowed to absorb amalgam.
It has been established that the more uniform the ore the smaller may be the samples; where the ore is spotty, the samples should be large, as is also the case where the ore is loose and breaks irregularly, or is alternately hard and soft. In cutting a sample the rich spots should be avoided if they are few in number; if there are many rich spots, the groove should include everything along its line. It is a very difficult matter to sample correctly a spotty ore. In the case of an ore that consists of poor mineralization carrying free gold, the average cannot well be determined by sampling; a majority of the samples of such an ore will be very low, or blanks, and a few will be very high; the average obtained will be more a matter of luck than a basis for an accurate estimate.
The best safeguard against salting is to decide upon a plan for safeguarding samples and never to make any exception in carrying it out, whatever the circumstances; if an engineer trusts his judgment as to whether he is in safe company, his judgment is almost certain to be at fault at some time during his career, but if he always maintains the same vigilance he will never be salted. Salting is the result of carelessness, and is inexcusable. The inclusion of waste samples is generally recommended as a safeguard, but like much good advice, is rarely carried out. The gold prospector should insists that no one except assistants whose integrity is known to him shall approach a sample until it is placed in a new, clean sack, and sealed, with the top turned over and tied down to prevent the working in of fine particles at the mouth of the sack.
As a check upon a series of samples so taken, it is well to save a portion of the fines from rejected quartering and to pan them; if a black greasy scum appears, it is evidence of tellurides; if a string of colors appears, its origin should be ascertained. After being sacked the samples should be locked in a mail sack, preferably made of leather, or in a trunk. If the sacks used are clean, a syringe cannot be used without detection through the stain left on the inside of the sack. It is much better to offend the vendors by the precautions taken than to run any chances of being salted; those with honest intent seldom take offense at such precautions.