From Wikipedia, the free encyclopedia
Jump to: navigation, search
Gormanite from the Doce valley, Minas Gerais, Brazil (size: 4.2 x 4.2 x 3.0 cm)
Category Phosphate minerals
(repeating unit)
Strunz classification 8.DC.45
Crystal system Triclinic
Crystal class Pedial (1)
H-M symbol: (1)
Space group P1
Unit cell a = 11.77, b = 5.11
c = 13.57 [Å]; α = 90.45°
β = 99.15°, γ = 90.05°; Z = 2
Color Blue green
Crystal habit Aggregates of acicular crystals; pseudomonoclinic
Twinning Polysynthetic around [010]
Cleavage {001} indistinct
Fracture Splintery
Tenacity Brittle
Mohs scale hardness 4-5
Luster Sub-vitreous, greasy
Streak Pale green
Diaphaneity Semitransparent
Specific gravity 3.10–3.13
Optical properties Biaxial (-)
Refractive index nα = 1.619 nβ = 1.653 nγ = 1.660
Birefringence .041
Pleochroism Strong, X colorless, Y blue, Z colorless
2V angle Measured: 53°
References [1][2][3]

Gormanite is a phosphate mineral with the formula (Fe,Mg)3Al4(PO4)4(OH)6·2H2O. It was named after the University of Toronto professor Donald Herbert Gorman (born 1922).


It was first described in 1981 for occurrences in Rapid Creek and Big Fish River in the Dawson Mining District, Yukon Territory, Canada. At the type localities it occurs as veins in iron phosphate nodules.[1][3] In the Bisbee, Arizona occurrence, it occurs as large crystals within fractures in a tonalite intrusive. It has also been reported from near Newport, Sullivan County, New Hampshire, and the Charles Davis pegmatite, Groton, Grafton County, New Hampshire. It also has been reported from the Tsaobismund pegmatite, south of Karibib, Namibia.[3]


  1. ^ a b Gormanite, MinDat.org, retrieved 2011-01-30 
  2. ^ Gormanite, WebMineral.com, retrieved 2011-01-30 
  3. ^ a b c Handbook of Mineralogy

External links[edit]