Ludlamite

Ludlamite
General
Category Phosphate mineral
Formula
(repeating unit)
(Fe,Mn,Mg)3(PO4)2·4H2O
Strunz classification 8.CD.20
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group P21/a
Unit cell a = 10.541(5), b = 4.646(4)
c = 9.324(5) [Å]; β = 100.52°; Z = 2
Identification
Color Apple-green to bright green
Crystal habit Tabular crystals; massive, granular
Cleavage Cleavage: perfect on {001}, indistinct on {100}
Mohs scale hardness 3.5
Luster Vitreous, pearly on cleavage
Streak Pale greenish white
Diaphaneity Translucent
Specific gravity 3.12–3.19
Optical properties Biaxial (+)
Refractive index nα = 1.650 - 1.653 nβ = 1.669 - 1.675 nγ = 1.688 - 1.697
Birefringence δ = 0.038 - 0.044
2V angle Measured: 82°
References [1][2][3]

Ludlamite is a rare phosphate mineral with formula: (Fe,Mn,Mg)3(PO4)2·4H2O.

It was first described in 1877 for an occurrence in Wheal Jane mine in Cornwall, England and named for English mineralogist Henry Ludlam (1824–1880).

Occurrence

It occurs in granite pegmatites and as a hydrothermal alteration product of earlier phosphate bearing minerals in a reducing environment.[3] It occurs associated with whitlockite, vivianite, triploidite, triplite, triphylite, siderite, phosphoferrite, fairfieldite and apatite.[1]

References

Media related to ludlamite at Wikimedia Commons

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