Beryllonite Locality: Beryllonite Locality, Stoneham , Oxford County, Maine , USA ( Locality at mindat.org ) Size: 2.4 x 2.1 x 0.8 cm. Beryllonite. Ex. John Manley Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Beryllonite
A rare sodium-beryllium phosphate forming transparent, colorless to pale-yellow tabular crystals.
Intro adapted from Wikipedia (CC BY-SA).
Beryllonite is an IMA-recognized mineral species in the phosphate class, with the chemical formula NaBe(PO₄).
It crystallizes in the monoclinic crystal system (space group P2_1/n). It is a member of the Beryllonite structural group.
Key properties: Mohs hardness 5.5–6; specific gravity 2.77–2.84; Vitreous to adamantine, may be pearly on {010} luster; refractive index 1.557; optically biaxial.
IMA symbol Bel, grandfathered status — known before the IMA’s founding, named in 1888.
Found as a rare secondary mineral in granitic and alkalic pegmatites.
It is found associated with Herderite, triplite, beryl, apatite, cassiterite, columbite, eosphorite, morinite, väyrynenite, lithiophilite, elbaite, pollucite, petalite, lepidolite.
The name refers to one of the major constituents in the composition, BERYLLium.