Gatehouseite 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 ...

hydroxy

phosphate Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...

mineral with formula Mn₅(PO₄)₂(OH)₄. First discovered in 1987, it was identified as a new mineral species in 1992 and named for Bryan M. K. C. Gatehouse (born 1932). , it is known from only one mine in

South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...

Description

Gatehouseite occurs as radiating or divergent groups of bladelike crystals up to 100 μm by 20 μm by 5 μm in size and as overgrowths on

arsenoclasite Arsenoclasite (originally arsenoklasite) is a red or dark orange brown mineral with formula Mn5(AsO4)2(OH)4. The name comes from the Greek language, Greek words ''αρσενικόν'' (for arsenic) and ''κλάσις'' (for cleavage (crystal), cle ...

that are up to 5 mm long. The transparent mineral can be brownish-orange or yellow in color. Gatehouseite is the

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

analogue of arsenoclasite. The mineral occurs in cavities in sedimentary iron and manganese deposits in association with

shigaite Shigaite is a mineral with formula NaAl3(Mn2+)6(SO4)2(OH)18·12H2O that typically occurs as small, hexagonal crystals or thin coatings. It is named for Shiga Prefecture, Japan, where it was discovered in 1985. The formula was significantly revised ...

hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...

hausmannite Hausmannite is a complex oxide, or a mixed oxide, of manganese containing both Divalent, di- and Trivalent, tri-valent manganese. Its chemical formula can be represented as , or more simply noted as , or , as commonly done for magnetite (), the co ...

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 ...

barite Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate (Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...

, and manganoan ferroan calcite. Based on a 1977 experiment that produced triploidite, it is likely that gatehouseite formed by a reaction between hausmannite and

basic Basic or BASIC may refer to: Science and technology * BASIC, a computer programming language * Basic (chemistry), having the properties of a base * Basic access authentication, in HTTP Entertainment * Basic (film), ''Basic'' (film), a 2003 film ...

phosphorus-rich fluids at low temperature and variable pH conditions.

History

In May 1987, Glyn Francis, an employee at the Iron Monarch mine in South Australia, submitted for identification some mineral specimens from the mine to A. Pring. Very small, unidentified pale brownish orange crystals were seen in one specimen; study showed they had a formula of the type ''M''₅(''X''O₄)₂(OH)₄ and contained

, and a minor quantity of

arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

. The

powder X-ray diffraction Powder diffraction is a scientific technique using X-ray, neutron, or electron diffraction on powder or microcrystalline samples for structural characterization of materials. An instrument dedicated to performing such powder measurements is cal ...

pattern could not be recorded as insufficient material was available. Another specimen in the same group consisted of arsenoclasite crystals overgrown by what appeared to be its as yet undescribed phosphorus analogue. Francis later discovered more of the brownish orange crystals in sufficient quantity to obtain an X-ray

diffraction pattern Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wav ...

. This proved that the crystals and the overgrowths were the same, new mineral species. Gathehouseite was named for Bryan Michael Kenneth Cummings Gatehouse for his contributions to the study of

oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

s and oxysalts. The Commission on New Minerals and Mineral Names recognized the mineral and approved its name in 1992 (IMA 1992-016). Due to the small size and intergrowth of the crystals,

single-crystal X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract in specific directions. By measuring the angles and ...

is difficult to perform on gatehouseite. In 2011, this technique was successfully used to determine the crystal structure of the mineral.

Distribution

The type material is housed at the

South Australian Museum The South Australian Museum is a natural history museum and research institution in Adelaide, South Australia, founded in 1856 and owned by the Government of South Australia. It occupies a complex of buildings on North Terrace in the cultur ...

in Adelaide and the

Museum of Victoria Museums Victoria is an organisation that includes a number of museums and related bodies in Melbourne. These include Melbourne Museum, Immigration Museum, Scienceworks, IMAX Melbourne, a research institute, the UNESCO World Heritage-listed Roya ...

in Melbourne. , the Iron Monarch open cut remains the only site from which gatehouseite is known.

Crystal structure

Gatehouseite has the

space group In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...

P2₁2₁2₁. The crystal structure consists of Mn(O, OH)₆

octahedra In geometry, an octahedron (: octahedra or octahedrons) is any polyhedron with eight faces. One special case is the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex. Many types of i ...

and PO₄

tetrahedra In geometry, a tetrahedron (: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular Face (geometry), faces, six straight Edge (geometry), edges, and four vertex (geometry), vertices. The tet ...

. The five manganese sites are occupied by manganese and small amounts of magnesium. The two phosphorus sites are occupied by phosphorus and small amounts of silicon and arsenic.

References

Bibliography

* *{{cite journal, last1=Pring, first1=A., last2=Birch, first2=W.D., year=1993, title=Gatehouseite, a New Manganese Hydroxy Phosphate from Iron Monarch, South Australia, journal=Mineralogical Magazine, volume=57, issue=387, pages=309–313, publisher=The Mineralogical Society, doi=10.1180/minmag.1993.057.387.13, bibcode=1993MinM...57..309P, s2cid=140568230, url=http://www.minersoc.org/pages/Archive-MM/Volume_57/57-387-309.pdf, access-date=May 22, 2012, archive-date=May 27, 2016, archive-url=https://web.archive.org/web/20160527121034/http://www.minersoc.org/pages/Archive-MM/Volume_57/57-387-309.pdf, url-status=dead

External links

Images of gatehouseite
from mindat.org Phosphate minerals Orthorhombic minerals Minerals in space group 19