Mineral Information and Data:

Mn2+Al2O4 [CNMNC approved formula]

Named for Galax, Virginia, USA, close to Bald Knob, North Carolina, and for the plant, galax, after which the town is named.

IMA status : Valid species (Pre-IMA 1932) Grandfathered
(8th edition) :  
  (07) Multiple Oxides
  (07.02) (A+ B++)2 X4 Spinel group
  (07.02.01) (Aluminum subgroup)
(10th edition) :
  (04) Oxides and Hydroxides
  (04.B) Metal:Oxygen = 3:4 and similar
  (04.BB) With only medium-sized cations
Crystal system: Cubic System
Point group (H-M): m3m (or 4/m 3 2/m) — hexoctahedral
Space group: Fd3m
Unit cell: a = 8.258Å, Z =8
Crystal Habit: As octahedra and rounded grains, to 0.5 mm; as exsolution blebs.
Twinning: On {111} as both twin and composition plane, the spinel law, probable.
Color: Black, red-brown, red to yellow; in transmitted light, golden yellow, brownish orange, mahogany-red, deep red to reddish black
Diaphaneity: Opaque; may be translucent in thin section.
Luster: Vitreous
Hardness (Mohs): 7.5
Measured Density: 4.234 g/cm3
Fracture: Conchoidal
Streak: Red-brown
Geologic Setting: In carbonate-rich, silica-undersaturated parts of metamorphosed manganese deposits.
Mineral Association: Alleghanyite, rhodonite, sonolite, spessartine, tephroite, kutnohorite, manganhumite, jacobsite, kellyite, alabandite (Bald Knob, North Carolina, USA); katoptrite, magnetite, manganostibite, magnussonite, tephroite, manganhumite, manganosite (Brattfors mine, Sweden)


Black granular galaxite with reddish alleghanyite and white kutnohorite.
Origin: Bald Knob, Alleghany County, North Carolina, USA.
Photo: Jeff Weissman