Gormanite
Current inventory:  0 gems
 

  
Gormanite was named in 1981 by B. Darko Sturman, Joseph A. Mandarino, Mary E. Mrose and P. J. Dunn to honor Donald Herbert Gorman (1922– ), exploration mineralogist and Professor of Mineralogy of the University of Toronto, Canada.

Discovered in 1977;   IMA status:  Valid (IMA approved 1981)

Chemistry

Chemical Formula:

Fe²⁺₃Al₄(PO₄)₄(OH)₆•2(H₂O)

Hydrated Iron Aluminum Phosphate Hydroxide

Molecular Weight:

793.43 gm

Composition:

Aluminum

13.60 %

Al

25.70 %

Al₂O₃

Iron

21.12 %

Fe

27.17 %

FeO

Phosphorus

15.62 %

P

35.78 %

P₂O₅

Hydrogen

1.27 %

H

11.35 %

H₂O

Oxygen

48.40 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Phosphate

Strunz 8th Ed. ID:

7/D.11-100

Nickel-Strunz 10th Ed. ID:

8.DC.45

8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H₂O
C : With only medium-sized cations, (OH, etc.):RO₄ = 1:1 and < 2:1

Related to:

Gormanite-Souzalite Series. Isostructural with Souzalite. The Fe2+ analogue of Souzalite.

Varieties:

None

Synonyms:

IMA 1977-030

Crystal Data

Crystallography:

Triclinic - Unknown or Uncertain Class

Crystal Habit:

Crystals are elongated along [010], with large {001}, giving a bladelike aspect, with smaller {100}, {102}, {102}, {010}, to 1 cm; commonly in radial aggregates.

Twinning:

Polysynthetic around [010], composition plane {001}, universal.

Physical Properties

Cleavage:

Poor/Indistinct on {001}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

4.0 - 5.0

Density:

3.10 - 3.13 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Blue-Green

Transparency:

Semi-Transparent to Opaque

Luster:

Vitreous

Refractive Index:

1.619 - 1.660  Biaxial  ( - )

Birefringence:

0.0410

Dispersion:

Strong to Very Strong; r < v or r > v

Pleochroism:

X = Z = colorless; Y = blue

Occurances

Geological Setting:

As low-temperature fracture fillings in phosphate-ironstones (Yukon Territory, Canada); in fractures in tonalite (Bisbee, Arizona, USA).

Common Associations:

Souzalite, Siderite, Ludlamite, Oxidized Vivianite, Arrojadite, Kryzhanovskite, Quartz (Yukon Territory, Canada); Chlorite, Calcite, Quartz (Bisbee, Arizona, USA).

Common Impurities:

None

Co-Type Locality:

Big Fish River, Dawson Mining District, Yukon Territory, Canada;
Rapid Creek, Dawson Mining District, Yukon Territory, Canada

Year Discovered:

1977; IMA approved 1981

View mineral photos:

Gormanite Mineral Photos and Locations

More Information

Mindat.org 
Webmineral.com

Gormanite is one of the new phosphate minerals being found from the hydrothermal phosphate deposits at the Rapid Creek, Big Fish River and Blow River areas in the Yukon Territory of Canada. Iron-rich Gormanite forms a series with Magnesium-rich Souzalite. Gormanite is a relatively new mineral having been discovered in 1977 and is somewhat rare. It forms attractive, colorful well formed crystals.

Gormanite is found at only a few localities; from Rapid Creek, Yukon Territory, Canada. In the USA, in large crystals at Bisbee, Cochise County, Arizona; in New Hampshire, from the G.E. Smith mine, Newport, Sullivan County and the Charles Davis pegmatite, Groton, Grafton County At the Tsaobismund pegmatite, 60 km south of Karibib, Namibia.
 

  
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