Gormanite
(Fe,Mg)3Al4(PO4)4(OH)6·2H2OIMA symbol Gm[1] Strunz classification 8.DC.45 Crystal system Triclinic Crystal class Pedial (1)
(same H-M symbol) 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 Identification 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 [2][3][4]
(same H-M symbol)
c = 13.57 [Å]; α = 90.45°
β = 99.15°, γ = 90.05°; Z = 2
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 (1922–2020).
Occurrence
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.[2][4] 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.[4]
References
- ^ 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.
- ^ a b Gormanite, Mindat.org, retrieved 2011-01-30
- ^ Gormanite, WebMineral.com, retrieved 2011-01-30
- ^ a b c Handbook of Mineralogy
External links
- OpticalMineralogy.org
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