Nickel. Nickel may be determined as follows: A little of the powdered ore taken up on the point of a penknife, and dissolved in a mixture of ten drops of nitric and five drops of muriatic acid, should be boiled over a lamp for a few minutes, and ten or twelve drops of water added. A small quantity of ferrocyanide of potash will throw down a whitish-green precipitate, indicating nickel.
Platinum. Platinum is a most refractory metal to treat, as it must be boiled for at least two hours in the mixture of muriatic and nitric acid, known as aqua regia. A small amount of alcohol is to be added to the solution, and the latter filtered. The platinum is precipitated with ammonia chloride.
Manganese. Manganese may be proved as follows: A few grains of powdered ore are placed in a test-tube, with three or four drops of sulphuric acid. Two or three grains of granulated lead or litharge being dropped in, the color will become pink should manganese be in the ore.
A preliminary examination of a mineral may be made with a pocket lens and a penknife. With the first, any conspicuous constituents may be recognized, while a scratch with the point of the latter will give an idea as to the softness or hardness of the mineral. Should much quartz (silica) be present, a sharp blow with the steel will cause sparks.
The next test should be with some ore powdered and held over a spirit flame. A drop or two of water and a drop of sulpho-cyanide of potash will reveal iron, should such be present, by a deep red coloration.
To another portion add one drop of hydrochloric acid, and a dense, curdy precipitate will indicate silver, if there be any.
Added to the same original nitric acid solution, several drops of ammonia water would detect copper by a blue color.
Antimony, tin, aluminum, zinc, cobalt and nickel, uranium and titanium are best shown by the blowpipe.
Carbonates, that is those minerals that contain carbon and oxygen in addition to the metal, effervesce when brought into contact with hydrochloric acid. Some sandstones have a small amount of lime carbonate, and must be tried under the lens, as the bubbles are microscopic. These tests are extremely useful, but by no means infallible, owing to so few ores being pure.
When the explorer wishes to know all the constituents of the ore he has found, he must analyze it. An analysis gives every substance in the ore. Such examinations may be either by the "dry" or "wet" methods, though usually the term "analysis" is restricted to the latter, and "fire assay" is used to describe the former. The wet assay for silver, lead or mercury is effected as follows: