Cattiite is a phosphate mineral. The mineral was first found in a veins of dolomite carbonatites veins at the bottom of the Zhelezny (Iron) Mine in the Kovdor massif, Kola Peninsula, Russia. Cattiite was tentatively identified as Mg₃(PO₄)₂•22H₂O, which as a high hydrate magnesium orthophosphate. Later structural studies, revealed the existence of two

polytypes In materials science, polymorphism describes the existence of a solid material in more than one form or crystal structure. Polymorphism is a form of isomerism. Any crystalline material can exhibit the phenomenon. Allotropy refers to polymorphism ...

named Mg₃(PO₄)₂•22H₂O-1A1 and Mg₃(PO₄)₂•22H₂O-1A2. The polytype, Mg₃(PO₄)₂•22H₂O-1A2, had both the mineral and the name of the mineral approved (2000-032) by the Commission on New Minerals and Mineral Names or the (CNMMN) of the

International Mineralogical Association Founded in 1958, the International Mineralogical Association (IMA) is an international group of 40 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 5000 plus known mineral species. Th ...

or the (IMA). The name was approved by the CNMMN and the IMA was cattiite. The mineral cattiite was named that in the honor of the Michele Catti, Professor of Physical Chemistry at the

University of Milano Bicocca The University of Milano-Bicocca ( it, Università degli Studi di Milano-Bicocca, UNIMIB) is a public university located in Milan, Italy, providing undergraduate, graduate and post-graduate education. Established in 1998, it was ranked by the ' ...

in Italy, because of his work on the crystal chemistry of hydrated oxy-salts.

Natural occurrence and localities

Cattiite bas been found in centimeter sized cavities that are within a 20–40 cm thick of the dolomite carbonatites that were enriched in late hydrothermal Mg-rich phosphates that was located at the Zhelezny Mine quarry. The vein of dolomite carbonatites that the cattiite is found cross-cuts

forsterite Forsterite (Mg2SiO4; commonly abbreviated as Fo; also known as white olivine) is the magnesium-rich end-member of the olivine solid solution series. It is isomorphous with the iron-rich end-member, fayalite. Forsterite crystallizes in the orthor ...

and magnetite ore that are located at the bottom of the mine's quarry. The mineral occurs as a mass that is up to 1.5 cm in size and usually contains a single crystal that fills the free space in the cavities and interstices of associated minerals. These associated minerals are

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

, nastrophite, bakhchisaraitsevite, sjogrenite, magnetite, and carbonate-fluorapatite. Cattiite is also mined in Western Australia, Chile, France, Namibia, and United Kingdom.

Properties

Crystallography

Cattiite is triclinic and has both very close cell parameters and crystal structures. The mineral has a space group of P. The structures of the mineral are based on an isolated PO₄ tetrahedra and Mg(H₂O)₆ octahedra that are joined by hydrogen bonds. The structures of the (001) sheets of the octahedra plus a sheet made of octahedra and tetrahedra form a polar (001) layer that is copied by a center of symmetry to form a layer with thickness that correlates with the c parameter. The X-ray single-crystal diffractometry of the mineral cattiite has a cell that is ''a'' = 6.932(2) Å, ''b'' = 6.925(3) Å, ''c'' = 16.154(5) Å, α = 82.21(4)°, β = 89.70(4)°, γ = 119.51(3)°, V = 666.3(3) Å³, and Z = 1.

Physical properties

Cattiite usually occurs as a mass of single crystals that are sometimes shown to be the dominant form on the axis. Along the axis is where the percent cleavage located at, while the uneven fractures are in other directions. Luster of cattiite is

vitreous Vitreous may refer to: Materials * Glass, an amorphous solid material ** Vitreous enamel, a material made by fusing powdered glass to a substrate by firing * Vitreous lustre, a glassy luster or sheen on a mineral surface Biology * Vitreous body, ...

, with a gypsum-like pearly sheen that is on the perfect cleavage planes {001}. The mineral is colorless and transparent. Cattiite has a Mohs hardness of 2 and also a

tenacity Tenacity may refer to: * Tenacity (psychology), having persistence in purpose * Tenacity (mineralogy) a mineral's resistance to breaking or deformation * Tenacity (herbicide), a brand name for a selective herbicide * Tenacity (textile strength) * ...

of being brittle. The specific gravity of cattiite is 1.65. The density of the mineral is 1.65 g/cm³ (measured) and 1.64 g/cm³ (calculated). It is non-pleochroic and bi-axial (-). The refractive index of the mineral is α = 1.459 (1), β = 1.470(1), and γ = 1.470(1). The optical orientation of cattiite is X ^ 01= 80°, Y ^ 00= 10°, and Z is perpendicular to 01 The minerals also has a weak dispersion, r < v.

Chemical properties

The high hydration that cattiite has makes it unstable under heating. There were thermal studies done that showed that Mg₃(PO₄)₂•22H₂O as a synthetic at 70 °C, was partially dehydrated. This dehydration of the mineral began occurring ar 40-60 °C depending on the relative humidity in the air. It is easily soluble in diluted cold 10% hydrochloric acid (HCl). Cattiite also loses water under a vacuum when it was studied under an electron microprobe.

References