Formula: Mn2+Mn2+2(PO4)2
Anhydrous phosphate, graftonite group, forms a series with
graftonite,
manganese-bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.60 to 3.70 measured, 3.71 calculated
Hardness: 5
Streak: Light pink
Colour: Reddish-Brown to pinkish brown
Environments
Beusite is a late-stage accessory mineral in complex granite pegmatites, and it
has also been found as euhedral inclusions in troilite nodules in an
iron meteorite
(Webmin, HOM).
The beusite-graftonite series, is restricted on Earth to pegmatites where beusite
is intergrown with other phosphates including triphylite and
lithiophilite. It represents a breakdown of a high-temperature phase
(AM 76.1985-1989).
Associated minerals include lithiophilite or
triphylite in pegmatites and troilite and
sarcopside in the iron meteorite (HOM).
Localities
Beusite is found in granite pegmatites in three localities in San Luis Province,
Argentina: Los Aleros, Amanda and San Salvador. Many of the pegmatites of the Sierra de San Luis contain
lithium and beryllium
minerals. All of them at which beusite or graftonite were found have commercial
amounts of spodumene, beryl or
muscovite. Lithiophilite interlaminated
with beusite was found in all the San Luis localities (AM 53.1799-1814).
At the type locality, the Los Aleros pegmatite, Coronel Pringles Department, San Luis Province, Argentina, beusite occurs in a
granite pegmatite associated with
triphylite and interlaminated with
lithiophilite (Mindat).
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, beusite occurs rarely in the margin of
lithiophilite masses. The Emmons pegmatite is an example of a highly evolved
boron-lithium-cesium-tantalum enriched pegmatite
(R&M 94.6.505).
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