Strontiowhitlockite

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Formula: Sr₉Mg(PO₃OH)(PO₄)₆
Anhydrous normal phosphate, whitlockite subgroup of the merrillite group, strontium-bearing mineral
Crystal System: Trigonal
Specific gravity: 3.64 measured, 3.60 calculated
Hardness: 5
Streak: White
Colour: White
Common impurities: Ca
Environments

Carbonatites

Although strontiowhitlockite was approved in 1989, to date (June 2023) it has been reported only from the Kovdor Massif.

Localities

The type locality, the Kovdor Zheleznyi mine, Kovdor Massif, Murmansk Oblast, Russia, is part of the Kovdor ultramafic alkaline complex. The elliptical complex is emplaced in gneiss and granitic gneiss and concentrically zoned; dunite and pyroxenised and phlogopitised dunite in the core give way to jacupirangite and melanocratic nephelinolite, melilite rocks, ijolite and other nepheline-pyroxene rocks, and an outer ring of fenite. The Kovdor magnetite-apatite-baddeleyite deposit is emplaced within the contact of ijolite with fenite. In general, the igneous rocks exposed in the mine are forsterite-magnetite (with apatite) ore-rocks and jacupirangite. Accessory baddeleyite is present in both forsterite-magnetite and carbonate-bearing ores.

Veins of carbonatite are widespread throughout the deposit and can be divided into the following groups:
1. Calcite carbonatites with forsterite and phlogopite,
2. Calcite carbonatites with tetraferriphlogopite,
3. Dolomite carbonatites with zircon,
4. Calcite-dolomite carbonatites with ilmenite.

The dolomite carbonatites containing zircon host strontiowhitlockite here. There is hydrothermal phosphate mineralisation after dolomite, including collinsite, bobierrite, vivianite and kovdorskite. A 60-m long vein of dolomite carbonatite that cross-cuts jacupirangite was exposed during mining operations, and includes numerous cm-sized cavities containing phosphates, including carbonate-rich fluorapatite, collinsite and bobierrite. Strontiorwhitlockite crystals up to 8 microns across were found in a cavity 1 cm across in the central zone of the vein, in association with aggregates of strontian collinsite, octahedral crystals of pyrite and rhombohedra of dolomite. An unnamed strontium-magnesium-CO₃-bearing hydrous phosphate is intimately intergrown with the strontiowhitlockite (CM 29, 87–93).
Other associated minerals include rimkorolgite (HOM).

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