Falsterite | |
---|---|
General | |
Category | Phosphate mineral |
Formula (repeating unit) | Ca2MgMn2+2(Fe2+0.5Fe3+0.5)4 Zn4(PO4)8(OH)4(H2O)14 |
IMA symbol | Fls[1] |
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 | [2][3] |
Falsterite is a rare phosphate mineral[3] with the formula Ca2MgMn2+2(Fe2+0.5Fe3+0.5)4Zn4(PO4)8(OH)4(H2O)14.[2] It is a pegmatitic mineral, related to the currently approved mineral ferraioloite.[3]
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.[2]
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.[2]
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.
- ^ a b c d 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
- ^ a b c "Falsterite: Falsterite mineral information and data". Mindat.org. Retrieved 2016-03-04.