Ludlamite

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

Ludlamite
General
CategoryPhosphate mineral
Formula
(repeating unit)
(Fe,Mn,Mg)3(PO4)2·4H2O
Strunz classification8.CD.20
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/a
Unit cella = 10.541(5), b = 4.646(4)
c = 9.324(5) [Å]; β = 100.52°; Z = 2
Identification
ColorApple-green to bright green
Crystal habitTabular crystals; massive, granular
CleavageCleavage: perfect on {001}, indistinct on {100}
Mohs scale hardness3.5
LusterVitreous, pearly on cleavage
StreakPale greenish white
DiaphaneityTranslucent
Specific gravity3.12–3.19
Optical propertiesBiaxial (+)
Refractive indexnα = 1.650 - 1.653 nβ = 1.669 - 1.675 nγ = 1.688 - 1.697
Birefringenceδ = 0.038 - 0.044
2V angleMeasured: 82°
References[1][2][3]

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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