Hydrated phosphate containing hydroxyl, forms a series with childrenite
Specific gravity: 3.06 to 3.08
Colour: Usually pale brown, golden brown, also medium brown to dark brown, occasionally pink or rose red
Solubility: Soluble in acids
Common impurities: Fe
Eosphorite is a secondary mineral in some phosphate-bearing granite
Common associates are fairfieldite and
At the type locality, the Fillow Quarry, Branchville, Redding, Fairfield county, Connecticut, USA, eosphorite occurs in a granite pegmatite, associated with rhodochrosite, lithiophilite, triploidite and dickinsonite (Dana, Mindat, HOM).
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, eosphorite occurs as an alteration product of lithiophilite associated with montebrasite. (R&M 94.6.507).
At Newry, Oxford county, Maine, USA, eosphorite is associated with albite, cookeite, apatite, beryllonite, hydroxylherderite and tourmaline (HOM).
The Consolidated quarry in Georgetown, Sagadahoc county, Maine, USA, is a granite pegmatite with lithium-rich zones. These contain cavities that may produce tourmaline and spodumene in association with lepidolite, beryl, fluorapatite, montebrasite, cassiterite, and columbite-tantalite group minerals. In a mineralised zone rich in albite, muscovite and beryl; some cavities were opened that mainly contained quartz crystals, beryl crystals to 10 cm, albite, microcline and muscovite. Many of these minerals were overgrown by eosphorite crystals to 3 mm. In addition, the interior portions of several of the beryl crystals exhibit alteration to secondary beryllium phosphates. Hydroxylherderite crystals to 2 cm are locally abundant and are typically coated by eosphorite crystals. The origin of the eosphorite is problematic, as no remnants of primary phosphate minerals (triphylite, lithiophilite, montebrasite-amblygonite, fluorapatite) were observed, although montebrasite can be abundant in some parts of the quarry (R&M 90-3.275).
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