Minyulite is a rare

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 ...

with a chemical formula of (redefinition, IMA21-E). It occurs as groups of radiating fine fibrous crystals within rock cracks of phosphatic

ironstone Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially. Not to be con ...

. Minyulite belongs to the orthorhombic crystal system. This indicates that it has three axes of unequal length yet all are perpendicular to each other. Its cell constants are a=9.35, b=9.74 c=5.52. As for its optical properties, Minyulite is an

anisotropic Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's phys ...

mineral which means the velocity of light differs when traveling through it depending on the cut of its cross-section which gives it more than one refractive index.Klein, C., and Dutrow, B.(2007) The 23rd Edition of the Manual of Mineral Science, 290 p. John Wiley and Sons, Inc. Hoboken, New Jersey, U.S.A. The mineral is optically biaxial. Its birefringence value is 0.007. It has three

refractive indices In optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of vi ...

which are nα=1.531 nβ=1.534 nγ=1.538. Refractive indices are a ratio of the speed of light in a median with respect to the speed of light passing through the mineral.

Occurrence

It was first described in 1933 for an occurrence in Western Australia and named after the

type locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

, Minyulo Well in

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to ...

. Minyulite is considered as a secondary phosphate since it is formed by the alteration of a primary phosphate. It occurs in association with dufrenite,

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 ...

fluellite Fluellite is a mineral with the chemical formula Al2(PO4)F2(OH)•7H2O. The name is from its chemical composition, being a ''fluate of alumine'' (French). It was first described in 1824 for an occurrence in the Stenna Gwyn Mine, St Stephen-in-Br ...

wavellite Wavellite is an aluminium basic phosphate mineral with formula Al3( P O4)2(O H, F)3·5 H2O. Distinct crystals are rare, and it normally occurs as translucent green radial or spherical clusters. Discovery and occurrence Wavellite was firs ...

variscite Variscite is a hydrated aluminium phosphate mineral (). It is a relatively rare phosphate mineral. It is sometimes confused with turquoise; however, variscite is usually greener in color. The green color results from the presence of small amounts ...

and

leucophosphite Leucophosphite is a phosphatic mineral derived from guano Guano (Spanish from qu, wanu) is the accumulated excrement of seabirds or bats. As a manure, guano is a highly effective fertilizer due to the high content of nitrogen, phosphate, a ...

. The mineral can be found in the underlying phosphatized rock zone of ornithogenic soil. Minyulite is not found in abundance, it can be found in the seashore of the maritime Arctic. Tatur, A., and Keck, A. (1990) Phosphates in ornithogenic soils of the Maritime Antarctic.Proc. NIPR Symp. Polar Biol: 3, 133-150.

References

{{Commonscat Phosphate minerals Orthorhombic minerals Minerals in space group 32 Potassium minerals Aluminium minerals