Mineralogists study them

Usage examples of ores.

It is also used for dissolving metals only from ores which contain metallic oxides not desired in the solution.

It is usual with quartzose ores to rely mainly on the action of carbonate of soda, but not entirely.

If the scorifier at the end of an operation is more than usually corroded, the borax should be replaced in subsequent assays on similar ores by powdered glass or quartz.

Silver is found in the ores of other metals, such as fahlerz, which sometimes contains from two to ten per cent.

With ores that produce a thick slag the addition of 5 grams of fluor spar will be an advantage.

With gold and silver ores, the proportion of precious metal is small, and it is necessary to carry the reduction to ozs.

In all those cases in which the slag retains an oxide of a heavy metal, this cleaning of the slag is advisable, and in the case of rich ores necessary.

The errors caused by these impurities are more marked in the determination of material having small quantities of metal than in that of ores which contain larger quantities.

It occurs native in sufficient quantity to constitute one of the chief ores of the metal.

It is present also in greater or less quantity in the ores of copper and zinc.

With rich ores such variation is unavoidable under any conditions, and the only safe plan is to take the mean of several assays.

But with poorer ores the accuracy of the assay, as well as convenience in working, is much increased by working in a crucible with larger charges.

And that with ores almost free from gangue some quartz or glass should be added to protect the crucible.

Except for ores rich in arsenic, it will be better to work with a solution one half this strength.

It is evident, therefore, that a charge of half an ounce or less of the ore, such as is usual with silver ores, would demand of the worker both skill and care in the handling of the minute quantity of gold to be obtained from it.