- © 2016 E. Schweizerbart'sche Verlagsbuchhandlung Science Publishers
Ferraioloite, MgMn2+4(Fe2+0.5Al3+0.5)4Zn4(PO4)8(OH)4(H2O)20, is a new secondary phosphate mineral from the Foote Lithium Company mine, Kings Mountain district, Cleveland County, North Carolina, USA. The mineral was found in tiny vughs within a thin seam of very fine-grained, sugary pegmatite with vivianite, fairfieldite/messelite, phosphophyllite, scholzite/parascholzite, rittmannite, mangangordonite, kingsmountite, kastningite and metaswitzerite. Ferraioloite crystals occur as very thin greenish grey to lemon yellow plates or blades up to about 0.2 mm in length, but no more than a few μm thick. Crystals are biaxial (–), with indices of refraction α = 1.575(calc), β = 1.5825(5), γ = 1.5835(5), 2V(meas.) = 40(5)°. Dispersion is weak: r > v, the orientation is: X ≈ a, Y = b, Z ≈ c and pleochroism: X, Z = colourless, Y = blue grey; Y > >. X ≈Z. The empirical formula (based on 56 O atoms pfu) is Ca0.21Mg0.50Mn2+4.16Fe2+2.05Al3+2.01Zn4.27P8.00H43.59O56. Ferraioloite is monoclinic, space group I2/m, with the unit-cell parameters: a = 25.333(3) Å, b = 6.299(1) Å, c = 15.161(3) Å, β = 90.93(3)° and V = 2419.0(2) Å3. Ferraioloite has a heteropolyhedral layer structure with layers parallel to (100) and with isolated Mg(H2O)6 octahedra and water molecules packing between the layers. The heteropolyhedral slabs have the same topology as falsterite, with Mn2+ replacing Ca2+ and with Al3+ substituting for Fe3+.