Augelite

Augelite
General
CategoryPhosphate mineral
Formula
(repeating unit)
Al2(PO4)(OH)3
IMA symbolAul[1]
Strunz classification8.BE.05
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Unit cella = 13.124(6), b = 7.988(5)
c = 5.0633(3) [Å]
β = 112.25(2)°; Z = 4
Identification
ColorColorless to white, may be yellowish to pale rose, greenish
Crystal habitTabular to prismatic or acicular crystals; massive
CleavagePerfect on {110}, good on {201}, imperfect on {001} and {101}
FractureUneven
TenacityBrittle
Mohs scale hardness4 – 4.5
LusterVitreous, pearly on {110} cleavage
StreakWhite
DiaphaneityTransparent
Specific gravity2.696
Optical propertiesBiaxial (+)
Refractive indexnα = 1.574 nβ = 1.576 nγ = 1.588
Birefringenceδ = 0.014
2V angleMeasured: 50°
References[2][3]

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.[4]

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.[2][3]

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.[2]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c Handbook of Mineralogy
  3. ^ a b Mindat.org
  4. ^ 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