Augelite

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Augelite
Augelite-au13c.jpg
Augelite from Peru size: 3 x 3 x 2.8 cm
General
Category Phosphate mineral
Formula
(repeating unit)
Al2(PO4)(OH)3
Strunz classification 08.BE.05
Crystal symmetry Monoclinic prismatic
H-M symbol: 2/m
Space group: B2/m
Unit cell a = 13.124(6) Å, b = 7.988(5) Å, c = 5.0633(3) Å; β = 112.25(2)°; Z = 4
Identification
Color Colorless to white, may be yellowish to pale rose, greenish
Crystal habit Tabular to prismatic or acicular crystals; massive
Crystal system Monoclinic
Cleavage Perfect on {110}, good on {201}, imperfect on {001} and {101}
Fracture Uneven
Tenacity Brittle
Mohs scale hardness 4 - 4.5
Luster Vitreous, pearly on {110} cleavage
Streak White
Diaphaneity Transparent
Specific gravity 2.696
Optical properties Biaxial (+)
Refractive index nα = 1.574 nβ = 1.576 nγ = 1.588
Birefringence δ = 0.014
2V angle Measured: 50°
References [1][2]

Augelite is an aluminium phosphate mineral with formula: Al2(PO4)(OH)3. The shade varies from colorless to white, yellow or rose. Its crystal system is monoclinic.[3]

It was first described by Christian Wilhelm Blomstrand for an occurrence in Västanå iron mine at Scania, Sweden in 1868 and derives its name from the Greek αύγή in reference to its pearly lustre.[1][2]

It occurs as a product of metamorphism of phosphate bearing peraluminous sediments and in high-temperature hydrothermal ore deposits. It occurs in association with attakolite, svanbergite, lazulite, hematite, trolleite, berlinite, rutile, pyrophyllite, baryte, arsenopyrite, stannite, pyrite, andorite, cassiterite and zinkenite.[1]

References[edit]

  1. ^ a b c Handbook of Mineralogy
  2. ^ a b Mindat.org
  3. ^ Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason, and Abraham Rosenzweig: "Dana's new mineralogy", p. 851. John Wiley & Sons, 1997
Augelite from the Dawson Mining District, Yukon, Canada