Berillonite

Beryllonite is a rare phosphate mineral with formula NaBePO4. The tabular to prismatic monoclinic crystals vary from colorless to white or pale yellowish, and are transparent with a vitreous luster. Twinning is common and occurs in several forms. It exhibits perfect cleavage in one direction. The hardness is 5.5 to 6 and the specific gravity is 2.8. Refractive indices are nα = 1.552, nβ = 1.558 and nγ = 1.561. A few crystals have been cut and faceted, but, as the refractive index is no higher than that of quartz, they do not make very brilliant gemstones.

Key facts

Mineral.gravity: 2.8
Mineral.name: Beryllonite
Mineral.category: Phosphate minerals
Mineral.image: Beryllonite.jpg
Mineral.imagesize: 260px
Mineral.caption: Beryllonite (whitish) with tourmaline variety indicolite (blue) from Paprok, Nuristan Province, Afghanistan. Specimen size 4 cm
Mineral.formula: NaBePO4
Mineral.IMAsymbol: Bel
Mineral.strunz: 8.AA.10
Mineral.dana: 38.01.05.01
Mineral.system: Monoclinic
Mineral.class: Prismatic (2/m) (same H-M symbol)
Mineral.symmetry: P21/n
Mineral.color: Colorless, white to pale yellow
Mineral.habit: Crystals tabular {010} to short prismatic also in spherical aggregates, fibrous, massive; orthorhombic pseudo-symmetry
Mineral.twinning: polysynthetic, contact and penetration twins; pseudo-hexagonal stellate forms
Mineral.cleavage: {010} perfect; {100} good, interrupted; {101} indistinct; {001} in traces
Mineral.fracture: Conchoidal