Anhydrous normal phosphate, alters to herderite (Mindat).
Specific gravity: 2.77 to 2.85
Hardness: 5½ to 6
Colour: Colourless, white, rarely pale light yellow; colourless in transmitted light.
Solubility: Slowly soluble in acids
Beryllonite is a rare secondary mineral in granitic and alkaline
pegmatites, associated with herderite,
albite, orthoclase and
At the Emmons pegmatite, Greenwood, Oxford county, Maine, USA, beryllonite has been found, but usually it has been replaced by such species as hydroxylherderite. The Emmons pegmatite is an example of a highly evolved boron-lithium-cesium-tantalum enriched pegmatite (R&M 94.6.505).
At the Dunton quarry, Newry, Oxford county, Maine, USA, beryllonite occurs with hydroxylherderite and elbaite (Dana).
At the type localities, Stoneham, Oxford county, Maine, USA, beryllonite occurs in a granite pegmatite associated with triplite, smoky quartz, muscovite, microcline, fluorapatite, cassiterite, beryl and albite. (Mindat, Dana). It is the oldest of the phosphates to form here, often coated with herderite, which is a product of its alteration (AM13.392).
At the Chickering Mine, Cheshire county, New Hampshire, USA, beryllonite crystals are found in small cavities of milky quartz and montebrasite, associated with apatite and muscovite (R&M 90-5.414).
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