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Formula: KAl2(PO4)2(OH).2H2O
Hydrated phosphate containing hydroxyl, leucophosphite group
Crystal System: Monoclinic
Specific gravity: 2.69 measured, 2.62 calculated
Hardness: 5
Streak: Pink
Colour: Deep red, colourless
Environments
Localities
At the type locality, the Tip Top Mine, Fourmile, Custer Mining District, Custer county, South Dakota, USA,
tinsleyite is moderately abundant, and is found in highly altered
triphylite pods within the intermediate zone
of the pegmatites. This zone consists of large feldspar
variety perthite crystals with quartz,
muscovite, fluorapatite,
albite, beryl, minor
elbaite and
columbite-tantalite. In most
cases, the triphylite has been totally altered to
secondary phosphates.
Rockbridgeite-frondelite and
tavorite are among the earliest
secondary phosphates formed with
rockbridgeite being dominant.
Leucophosphite crystals about 5 mm in length formed subsequent to
rockbridgeite-frondelite and
tavorite. Tinsleyite formed after
leucophosphite on which it commonly occurs as morphologically
continuous overgrowths. Spherical aggregates of robertsite, together with
prismatic crystals of a jahnsite-group mineral, formed subsequent to
leucophosphite and tinsleyite. Other minerals younger than
tinsleyite include carbonate-rich apatite and
laueite
(AM 69.374-376).
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