Manganese ore specific weight and impurities

Manganese occurs in more than a hundred different crystalline rocks around the globe. Like iron, it dissolves and is deposited again as compounds such as carbonates, oxides and oxide hydrates.

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.