Afmite

afmite

matulaite

variscite

kobokoboite

Images

Formula: Al₃(OH)₄(H₂O)₃(PO₄)(PO₃OH).H₂O
Hydrated phosphate
Crystal system: Triclinic
Specific gravity: 2.39 measured, 2.391 calculated for the empirical formula, 2.394 calculated for the ideal formula
Hardness: 1½
Streak: White
Colour: Colourless to white, weathering to cream or yellowish
Luminescence: Not fluorescent under UV
Environments

Hydrothermal environments

Afmite is a secondary mineral formed by remobilisation and crystallisation during low-temperature hydrothermal activity and/or weathering and ground water activity (HOM).

Localities

At the Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo, afmite is associated with kobokoboite (HOM).

At the type locality, the Phosphate occurrence, Fumade, Fontrieu, Castres, Tarn, Occitanie, France, afmite occurs, sometimes in association with matulaite and variscite, in fractures and solution cavities in shale/siltstone. The formation is probably largely the result of remobilisation and crystallisation during low-temperature hydrothermal activity and/or weathering and ground water activity. Afmite forms in cockscomb aggregates of diamond-shaped tablets, ubiquitously contact-twinned and also commonly twinned by rotation, forming star-like sixlings. The streak is white and the lustre is pearly. The mineral is flexible, but not elastic, has an irregular fracture and three cleavage directions, one perfect and two good (EJM 23.2.269-277).
Afmite from Fumade - Image

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