Chemical properties of Manganese

Manganese is a silvery-gray metal that resembles iron. See Figure 1 for its specific chemical properties. It is hard and very brittle and difficult to fuse. It has 25 electrons arranged in an electronic configuration of [Ar]3d5 4s2 . All the seven electrons in the 4s and 3d subshells can be involved in reactions; thus manganese can have oxidation states up to 17 in its compounds. The full range of oxidation states is 23 to 17 but 12 is the most stable. Oxidation states of 12, 14 and 17 are common as exemplified by manganese ion (Mn²⁺), manganese(IV) oxide (MnO2), and permanaganate ion (MnO^- 4 ), respectively. Compounds in which manganese have the 15 and 16 oxidation states are prone to disproportionation reactions.

Mn is a major component of low-cost stainless steel. Ferromanganese (typically B80% Mn) is the intermediary in many current processes. Small Mn quantities improve the workability of steel at high temperatures as they form a high-melting sulfide and inhibit the formation of a liquid Fe sulfide at the grain boundaries. When the Mn concentration reaches 4%, the embrittlement of the steel turns into a dominant feature. The embrittlement decreases at higher Mn contents and gets to an acceptable level at 8%. Steel with 8% 15% of Mn shows a high tensile strength as high as 863 MPa.

Main mineral materials

Manganese is a relatively common element in minerals, with more than 650 minerals known that (can) contain this element. Within the elements class 2 silicide minerals are found, brownleeite (MnSi) and mavlyanovite (Mn5Si3). The sulfide class contains 11 different minerals with Mn, including minerals such as alabandite (MnS), hauerite (MnS2), and samsonite (Ag4MnSb2S6). The chlorides are represented by three minerals, chlormanganokalite (K4[MnCl6]), kempite (Mn21 2 OH e T3Cl), and scacchite (MnCl2).

More than 80 minerals are known in the oxide class, including some wellknown minerals such as birnessite ((Na,Ca)0.5(Mn4+,Mn3+)2O4· 1.5H2O), bixbyite (Mn³⁺ ₂ O3) (Fig. 2), hu¨bnerite (MnWO4) (Fig. 3), manganite (Mn³⁺O(OH)) (Fig. 4), and wodginite (Mn2+Sn4+Ta2O8) (Fig. 5). The carbonate class consists of 14 minerals with Mn in their structure, for example, kutnohorite (CaMn2+(CO3)2) and rhodochrosite (MnCO3) (Fig. 6). Within the borate class 15 minerals are known to contain Mn, such as sussexite (Mn21BO2(OH)). The sulfates are represented by 17 different minerals, including apjohnite (Mn2+Al2(SO4)4· 22H2O), moorhouseite ((Co,Ni,Mn)SO4· 6H2O), and sturmanite (Ca6(Fe3+,Al,Mn3+)2(SO4)2[B(OH)4](OH)12· 25H2O). Nearly 150 minerals are known in the phosphate class to contain Mn, examples are eosphorite (Mn2+Al(PO4)(OH)2· H2O), fairfieldite (Ca2Mn2+(PO4)2· 2H2O), hureaulite ((Mn,Fe)5(PO4)2(HPO4)2· 4H2O), lithiophilite (LiMn2+PO4), and strunzite (Mn²⁺Fe³⁺ ₂ (PO4)₂ (OH)₂· 6H2O) (Fig. 7). Nearly 250 minerals are found in the silicate class with Mn in their crystal structure. These include minerals such as babingtonite (Ca2(Fe,Mn)FeSi5O14(OH)), bustamite (CaMn2+(Si2O6)) (Fig. 8), inesite (Ca2(Mn,Fe)7Si10O28(OH)2·5H2O) (Fig. 9), olmiite (CaMn2+[SiO3(OH)](OH)), rhodonite (Mn²⁺SiO3) (Fig. 10), and tephroite (Mn²⁺ ₂ SiO4). Finally, two organic compounds are known with Mn, falottaite (MnC2O4· 3H2O) and lindbergite (Mn(C2O4)· 2H2O).

FIGURE 6. Rhodochrosite, MnCO3, a large pink rhombohedral crystal to 1.3 cm on edge perched perfectly at the center with several smaller crystals within the same vug lined with drusy quartz, SiO2.