Cadmium, Indium, Germanium, Gallium

Cadmium, Indium, Germanium, Gallium

All of these metals are by-products of treating zinc ore. No ore is mined primarily for its cadmium content but zinc ores rich in cadmium are treated preferentially and command a premium. Indium has important industrial uses and may become still more important. Little germanium and gallium are used at present but they are said to have future possibilities.

Cobalt

The ores are cobaltite (CoAsS), Smaltite (CoAs2) and a number of sulpharsenide minerals, which can be concentrated by gravity and flotation, but the ore in the Belgian Congo consists of hydrous black oxides. Concentrates are quoted per pound of contained cobalt and should carry at least 10% Co. The mines in the Belgian Congo are so productive that few small producers can compete.

Chromium

The only commercially important chromium mineral is chromite, a member of the spinel group. The general formula is R”O.R” 2O3. Practically speaking the formula fot chromite is best written (Fe,Mg) O.-(Fe, Al, Cr)2O3. Part of the ferric iron is usually replaced by magnesium and some of the chromium by alumina or ferrous iron with the result that the average pure chromite contains from 45% to 55% Cr2O3 and in many places the chromium content is even much less.

In considering the quality of a chromium ore the important variables are Cr2O3 content, chromium-iron ratio, SiO2 content, content and ratio of Al2O3 and MgO and sometimes the minor constituents such as sulphur, phosphorus and others if they exceed a fraction of 1%.

The physical characteristics of the ore are likewise extremely important particularly with respect to metallurgical lump ore and refractory lump ore. Lump ore is defined as that in which all lumps will pass a 6 inch screen and not more than 2 5 % will pass a 1/2 inch mesh screen.

From a market and usability basis, chrome ores are divided into three classes namely metallurgical, chemical and refractory. The primary distinction between metallurgical and chemical ores is the chrome-iron ratio which must be above 2.5 to 1 in metallurgical ores and which is 2.0 to 1 or less in chemical ores. This chemical distinction is accentuated by a marked price difference between the two classes. Refractory ores are characterized by a lower Cr2O3 content, higher Al2O3, FeO, MgO and particularly by their physical characteristics. Lime is especially detrimental in refractory ores. Standard specifications of these three types are as follows:

Metallurgical ore is used in making ferrochrome. Under standard American practice, the ore fed to the standard reduction furnace must contain a minimum of 70% lump, the balance being fines or concentrates. Certain processes can use a higher percentage of concentrates. The price of such ore is usually based on 48% Cr2O2 at a ratio of 3 to 1 with premium and penalties on Cr2O3, chrome-iron ratio, and penalties on silica.

Chemical ore is used in the manufacture of chrome chemicals. Prices are based on contained units of Cr2O3 with a penalty on silica.

Refractory ores are used in the manufacture of refractory bricks and refractory patching compounds. Prices are on a per ton basis depending on the known characteristics of a given ore.