Mineral Information and Data:

Al2PO4(OH)3 [CNMNC approved formula]

Named from the Greek αυγή ("auge") for "shine" or "luster," in allusion to the appearance of its cleavage surfaces.

IMA status : Valid species (Pre-IMA 1868) Grandfathered
(8th edition) :  
  (41) Anhydrous Phosphates Containing Hydroxyl or Halogen
  (41.06) where (A)2 (XO4) Zq
(10th edition) :
  (08) Phosphates, Arsenates, Vanadates
  (08.B) Phosphates, etc. with Additional Anions, without H2O
  (08.BE) With only medium-sized cations, (OH, etc.):RO4 > 2:1
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 13.124(6) Å, b = 7.988(5) Å, c = 5.0633(3) Å ; β = 112.25(2)°
Crystal Habit: As thick tabular crystals, {001}, to 13 cm, may be prismatic, even acicular parallel to [001], showing many forms, dominantly {110}, {001}, {201}, {111}, with {110} striated k [001]; may be massive.
Color: Colorless to white, may be yellowish to pale rose, greenish; colorless in transmitted light
Diaphaneity: Transparent
Luster: Vitreous, pearly on perfect {110} cleavage
Hardness (Mohs): 4.5 - 5
Measured Density: 2.696 g/cm3
Cleavage: 4; {110}, perfect; {201}, good; {001} and {101}, imperfect
Tenacity: Brittle
Fracture: Uneven
Streak: White
Geologic Setting: Formed by hydrogen metamorphism of phosphate-bearing rocks in peraluminous sediments; in some high-temperature hydrothermal ore deposits.
Mineral Association: Attakolite, svanbergite, lazulite, hematite, trolleite, berlinite (Vastan°a mine, Sweden); lazulite, rutile, pyrophyllite, barite (Champion mine, California, USA); arsenopyrite, stannite, pyrite, andorite, cassiterite, zinkenite (Bolivia)
Other Properties: Gemstone Extremely Rare.