Eosphorite is a brown (occasionally pink)

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

hydrous

phosphate mineral Phosphate minerals contain the tetrahedrally coordinated phosphate (PO43−) anion along sometimes with arsenate (AsO43−) and vanadate (VO43−) substitutions, and chloride (Cl−), fluoride (F−), and hydroxide (OH−) anions that also fit i ...

with

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

: Mn Al( P O₄)(O H)₂· H₂O. It is used as a gemstone. Eosphorite crystallizes in the

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

crystal system In crystallography, a crystal system is a set of point groups (a group of geometric symmetries with at least one fixed point). A lattice system is a set of Bravais lattices. Space groups are classified into crystal systems according to their po ...

. It forms slender prismatic crystals which often form radiating or spherical clusters. The crystals often show pseudo–

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

forms due to twinning. Eosphorite forms a series with

childrenite Childrenite is a rare hydrated phosphate mineral with elements iron, manganese, aluminium, phosphorus, oxygen and hydrogen. Its chemical formula is and it has a molecular weight of 229.83 g/mol. Its specific gravity is 3.2 and it has a Mohs hard ...

, the iron rich member, with divalent iron replacing most of the manganese in the crystal lattice. The two endmembers are isostructural but differ in their properties, such as crystal habit, coloration, and optical properties. It was first described in 1878 for an occurrence in the Branchville Mica Mine in Branchville,

Fairfield County, Connecticut Fairfield County is a County (United States), county in the southwestern corner of the U.S. state of Connecticut. It is the List of counties in Connecticut, most populous county in the state and was also its fastest-growing from 2010 to 2020. A ...

, US. Its name is derived from the Greek έωσφορος for "dawn-bearing," because of its pink color. It occurs worldwide typically as a secondary mineral in phosphate rich granitic

pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...

s in association with

rhodochrosite Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. In its (rare) pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. It streaks white, and its Mohs hardness varies bet ...

, lithiophilite,

triphylite Triphylite is a lithium iron(II) phosphate mineral with the chemical formula LiFePO4.IMA-CNMNC List of Miner ...

triploidite Triploidite is an uncommon manganese iron phosphate mineral with formula: . It crystallizes in the monoclinic crystal system and typically occurs as elongated and striated slender prisms which may be columnar to fibrous. Its crystals may be pink ...

, dickinsonite,

albite Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. It represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula . It is a tectosilicate. I ...

, cookeite,

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common e ...

, beryllonite, hydroxyl-

herderite Herderite is a phosphate mineral belonging to the apatite, phosphate group, with formula CaBe(PO4)(F,OH). It forms monoclinic crystals, often twinned and variable in colour from colourless through yellow to green. It forms a series with the more ...

, and

tourmaline Tourmaline ( ) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is a gemstone and can be found in a wide variety of colors. The ...

. An attractive combination of eosphorite and

rose quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

occurs at Taquaral, Minas Gerais, Brazil.

References

Phosphate minerals Orthorhombic minerals Minerals in space group 64 Gemstones {{phosphate-mineral-stub