Falsterite

Falsterite
Falsterite
General
Category	Phosphate mineral
Formula	Ca2MgMn2+2(Fe2+0.5Fe3+0.5)4 ; Zn4(PO4)8(OH)4(H2O)14
IMA symbol	Fls
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) ; (same H-M symbol)
Space group	P21/c
Unit cell	a = 6.39, b = 21.26 ; c = 15.37 [Å]; β = 90.56° (approximated); Z = 2
Identification
Color	Greenish-blue
Crystal habit	thin plates, rectangular laths
Cleavage	{010}, perfect
Fracture	Uneven
Luster	Vitreous
Streak	Very pale greenish-blue
Diaphaneity	Transparent
Density	2.78 (measured); 2.84 (calculated; approximated)
Optical properties	Biaxal (-)
Refractive index	nα=1.58, nβ=1.60, nγ=1.61 (approximated)
Pleochroism	Colorless to very pale yellow (X & Z), blue-green (Y)
Dispersion	Strong
References

Falsterite is a rare phosphate mineral with the formula Ca₂MgMn²⁺₂(Fe²⁺_0.5Fe³⁺_0.5)₄Zn₄(PO₄)₈(OH)₄(H₂O)₁₄. It is a pegmatitic mineral, related to the currently approved mineral ferraioloite.

Occurrence and association

Falsterite was found in Palermo No. 1 pegmatite, North Groton, Grafton County, New Hampshire, US. Co-type locality is pegmatite at Estes quarry, Baldwin, Cumberland County, Maine, US. Falsterite is a product of alteration of triphylite and sphalerite.

Crystal structure

Main features of the crystal structure of falsterite, which is somewhat similar to that of schoonerite, are:

chains of Feⁿ⁺O₆ octahedra, displaying edge-sharing
chains of ZnO₄ tetrahedra, that display corner-sharing
sheets, parallel to {010}, formed by linking the above two types of chains by PO₄ tetrahedra
slabs formed by linking the sheets with MnO₆ octahedra and CaO₇ polyhedra

The slabs are bridged by dimers of MgO₆ octahedra that display edge-sharing. Magnesium-bearing octahedra share edges with zinc-bearing tetrahedra.

References

↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
1 2 3 4 Kampf, A.R., Mills, S.J., Simmons, W.B., Nizamoff, J.W., and Whitmore, R.W., 2012. Falsterite, Ca₂MgMn²⁺₂(Fe²⁺_0.5Fe³⁺_0.5)₄Zn₄(PO₄)₈(OH)₄(H₂O)₁₄, a new secondary phosphate mineral from the Palermo No. 1 pegmatite, North Groton, New Hampshire. American Mineralogist 97(4), 496-502
1 2 3 "Falsterite: Falsterite mineral information and data". Mindat.org. Retrieved 2016-03-04.

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[1] Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.

[K-2] 1 2 3 4 Kampf, A.R., Mills, S.J., Simmons, W.B., Nizamoff, J.W., and Whitmore, R.W., 2012. Falsterite, Ca₂MgMn²⁺₂(Fe²⁺_0.5Fe³⁺_0.5)₄Zn₄(PO₄)₈(OH)₄(H₂O)₁₄, a new secondary phosphate mineral from the Palermo No. 1 pegmatite, North Groton, New Hampshire. American Mineralogist 97(4), 496-502

[Mindat-3] 1 2 3 "Falsterite: Falsterite mineral information and data". Mindat.org. Retrieved 2016-03-04.