Rhodonite is a

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

inosilicate, with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

(Mn, Fe, Mg, Ca)SiO₃, and member of the pyroxenoid group of

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s, crystallizing in the triclinic system. It commonly occurs as cleavable to compact masses with a rose-red color (its name comes ), often tending to brown due to surface

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

. The rose-red hue is caused by the manganese cation (Mn). Rhodonite

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s often have a thick tabular habit, but are rare. It has a perfect, prismatic cleavage, almost at right angles. The

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by Pressing (metalworking), pressing or abrasion ...

is 5.5–6.5, and the specific gravity is 3.4–3.7; luster is vitreous, being less frequently pearly on cleavage surfaces. The manganese is often partly replaced by

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

, calcium, and sometimes

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

, which may sometimes be present in considerable amounts; a greyish-brown variety containing as much as 20% of calcium oxide is called '' bustamite''; ''fowlerite'' is a zinciferous variety containing 7% of zinc oxide. The

inosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, the crystalline forms of silica (silicon dio ...

(chain silicate) structure of rhodonite has a repeat unit of five silica tetrahedra. The rare polymorph '' pyroxmangite'', formed at different conditions of pressure and temperature, has the same chemical composition but a repeat unit of seven tetrahedra. Rhodonite has also been worked as an ornamental stone. In the iron and manganese mines at Pajsberg near Filipstad and Långban in

Värmland Värmland () is a ''Provinces of Sweden, landskap'' (historical province) in west-central Sweden. It borders Västergötland, Dalsland, Dalarna, Västmanland, and Närke, and is bounded by Norway in the west. Name Several Latinized version ...

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

, small brilliant and translucent crystals (pajsbergite) and cleavage masses occur. Fowlerite occurs as large, rough crystals, somewhat resembling pink

feldspar Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...

, with franklinite and zinc ores in granular

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

at Franklin Furnace in

New Jersey New Jersey is a U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

. Rhodonite is the official

gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...

of the Commonwealth of Massachusetts.General Laws of Massachusetts, Chapter 2, Section 15
.

References

{{Gemstones Gemstones Manganese(II) minerals Iron(II) minerals Magnesium minerals Calcium minerals Pyroxene group Triclinic minerals Minerals in space group 2

See also

References