Beryllonite

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Beryllonite
Beryllonite.jpg
Beryllonite (whitish) with tourmaline variety indicolite (blue) from Paprok, Nuristan Province, Afghanistan. Specimen size 4 cm
General
Category Phosphate minerals
Formula
(repeating unit)
NaBePO4
Strunz classification 08.AA.10
Dana classification 38.01.05.01
Identification
Color Colorless, white to pale yellow
Crystal habit Crystals tabular {010} to short prismatic also in spherical aggregates, fibrous, massive
Crystal system Monoclinic - Prismatic H-M Symbol (2/m) Space Group: P 21/n (Marked orthorhombic pseudo-symmetry)
Twinning polysynthetic, contact and penetration twins; pseudo-hexagonal stellate forms
Cleavage {010} perfect; {100} good, interrupted; {101} indistinct; {001} in traces
Fracture Conchoidal
Tenacity Brittle
Mohs scale hardness 5.5 - 6
Luster Vitreous to adamantine, may be pearly on {010}
Streak White
Diaphaneity Transparent to translucent
Specific gravity 2.8
Optical properties Biaxial (-)
Refractive index nα = 1.552 nβ = 1.558 nγ = 1.561
Birefringence δ = 0.009
2V angle 68°
References [1][2][3]

Beryllonite is a rare sodium beryllium 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 lustre. 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.[4]

It occurs as a secondary beryllium mineral in granitic and alkalic pegmatites. It was first described from complex crystals and as broken fragments in the disintegrated material of a granitic vein at Stoneham, Oxford County, Maine where it is associated with feldspar, smoky quartz, beryl and columbite. It was discovered by James Dwight Dana in 1888, and named beryllonite for its beryllium content.

References[edit]

  1. ^ http://rruff.geo.arizona.edu/doclib/hom/beryllonite.pdf Handbook of Mineralogy
  2. ^ http://www.mindat.org/min-644.html Mindat.org
  3. ^ http://www.webmineral.com/data/Beryllonite.shtml Webmineral data
  4. ^ Public Domain One or more of the preceding sentences incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). "Beryllonite". Encyclopædia Britannica 3 (11th ed.). Cambridge University Press. p. 818. 
  • Palache, C., H. Berman, and C. Frondel (1951) Dana’s system of mineralogy, (7th edition), v. II, pp. 677–679