Deloneite

deloneite

belovite

lomonosovite

fluorcaphite

Formula: (Na_0.5REE_0.25Ca_0.25)(Ca_0.75REE_0.25)Sr_1.5 (CaNa_0.25REE_0.25)(PO₄)₃F_0.5(OH)_0.5
Phosphate, belovite group, apatite supergroup
Crystal System: Trigonal
Specific gravity: 3.92 measured, 3.95 calculated
Hardness: 5
Streak: White
Colour: Bright yellow
Solubility: Readily soluble in 10% hydrochloric or nitric acid at room temperature (Mindat)
Environments

Pegmatites

At the type locality, the Koashva Open Pit, Khibiny Massif, Murmansk Oblast, Russia, deloneite occurs in the natrolite core of a pegmatite, associated with fluorcaphite, belovite-(Ce), lomonosovite, sitinakite and fluorite (HOM, Mindat, AM 82.820).

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