Manganese ore specific weight and impurities

Manganese occurs in many minerals and rocks around the world. Like iron, it can pass into solution and then precipitate again as oxides, hydroxides, carbonates and silicates.

Manganese ore deposits can be:

• primary deposits: silicate minerals; they are large but decompose quickly under the action of water;

• secondary deposits: sedimentary, formed through the decomposition of other rocks.

Often a deposit consists of several manganese ores with different Mn content, from 5% to 56%. Ores also contain Fe, or iron, up to 40%, silica up to 30% and alumina up to 10%; P, or phosphorus, S, or sulfur, Ag, or silver, and other elements may occur in small quantities. Manganese ore contains a large percentage of moisture, often more than 10%.

The most economically significant ores with constant composition are:

• pyrolusite, oxides;

• braunite;

• manganite;

• psilomelane;

• hausmannite;

• rhodochrosite, carbonate;

• rhodonite, silicate;

• bementite;

• and others.

Manganese ores may have variable composition:

• manganese-iron ores with Mn content from 5% to 40%;

• black ocher;

• manganese-iron zinc;

• silver ore with high manganese content.

Impurities in Manganese Ores

Manganese ores contain a large number of different impurities, among which the following groups are distinguished:

• metals: these include iron, zinc, silver, tungsten, nickel and copper;

• gangue impurities that form slags, into which part of the manganese also passes;

• volatile impurities, such as carbon dioxide formation during melting of manganese spar;

• other impurities. This category includes sulfur and phosphorus, present in manganese ores at less than 1%. They are considered harmful, and in some cases iron may also be an undesirable impurity.

The main share of manganese ore consumption is in metallurgy, about 95%, while the rest is used in the chemical industry. Therefore, when developing a deposit, the main emphasis is placed on whether the rock meets the following chemical requirements:

• Mn content in the rock should be as high as possible so that extraction is economically justified. Depending on ore type and grade, its percentage may start from 20%;

• low content of harmful impurities;

• small amount of silica in the gangue.

The physical properties of the ore are now of minor importance, because manganese ore is not used in an unenriched state.