Mineral Information and Data:

Axinite-(Mn)
Ca4Mn2+2Al4[B2Si8O30](OH)2 [CNMNC approved formula]

Named for the dominant manganese in a mineral of the axinite group, and from the Greek for axe after their sharp crystal forms. First published in 1909. Named changed from manganaxinite (IMA, 2008).

IMA status : Renamed IMA Approved; 2008 ()
CLASSIFICATION 
Dana
(8th edition) :
56.02.02.03  
  (56) Sorosilicate Si2O7 Groups and O, OH, F. and H2O
  (56.02) with cations in [4] and/or >[4] coordination
  (56.02.02) Axinite group
  
Nickel-Strunz
(10th edition) :
09.BD.20
  (09) Silicates
  (09.B) Sorosilicates (dimer) structures
  (09.BD) Si2O7 groups, with additional anions; cations in tetrahedral [4] and greater coordination
  
Crystal system: Triclinic System
Point group (H-M): 1 — pinacoidal
Unit cell: a = 7.16Å, b = 9.19Å, c = 8.97Å; α = 88.26°, β = 82.8°, γ = 77.26°
Crystal Habit: Crystals typically flattened, axe-head-shaped, to 10 cm; granular, massive.
  
Color: Honey-yellow, clove-brown, brown, blue; colorless to pale brown or blue in thin section
Diaphaneity: Transparent to translucent
Luster: Vitreous
Hardness (Mohs): 6.5 - 7
Measured Density: 3.314 g/cm3
Cleavage: Good on {100}, poor on {001}, {110}, and {011}
Tenacity: Brittle
Fracture: Uneven to conchoidal
  
Polymorphism and Series: Forms two series, with axinite-(Fe), and with tinzenite.
Geologic Setting: Typically a mineral formed by contact metamorphism and boron metasomatism; from a pegmatite vein cutting metamorphosed iron formation at a contact with gabbro (Minnesota, USA).
Mineral Association: Chlorite, quartz, potassic feldspar
  
Synonyms/varieties: Manganaxinite
Other Properties: Gemstone Readily Available.

 

Axinite-(Mn)
Specimen has numerous blaced crystals of yellow axinite-(Mn)
covered with calcite. There are also grains of willemite.
Origin: Franklin, Sussex Co., New Jersey, U.S.A.
Sample size: 5 x 4 x 3.5 cm
Photo: John Veevaert, Trinity Mineral Co.

 

Axinite-(Mn)
(zoom-in of above)

 

Axinite-(Mn)
Cloved-brown axinite-(Mn) crystals.
Origin: Dal'negorsk, Primorskiy Kray, Russia
Sample size: 7 x 6.5 x 4 cm matrix
Photo: Dan Weinrich

 

Axinite-(Mn)
(zoom-in of above)

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