Segelerite

segelerite

collinsite

hydroxylapatite

robertsite

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Formula: CaMgFe³⁺(PO₄)₂(OH).4H₂O
Hydrates phosphate containing hydroxyl, overite group
Crystal System: Orthorhombic
Specific gravity: 2.67 measured, 2.610 calculated
Hardness: 4
Streak: White
Colour: Pale yellow-green to colourless
Environments

Pegmatites

Segelerite is a rare alteration product of triphylite in zoned complex granite pegmatites (HOM).

Localities

At the Mount Deverell variscite deposit, Milgun Station, Western Australia, segelerite has been found encrusting a cavity in oxidised siltstone that contains quartz and goethite-hematite and is overgrown by hydroxylapatite. The variscite deposits are hosted by marine sedimentary rocks (AJM 20.2.29).

At the type locality, the Tip Top Mine, Fourmile, Custer Mining District, Custer county, South Dakota, USA, segelerite occurs in moderate abundance as a late stage product in corroded triphylite-heterosite-ferrisicklerite-rockbridgeite masses; it occurs along joint fractures in dense ferrisicklerite-rockbridgeite, usually in close association with collinsite, minor hydroxylapatite and globules of robertsite (AM 59.48-59)

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