Mineral Information and Data:

Mn2+5(AsO4)2(OH)4 • 4H2O [CNMNC approved formula]

Named after the Greek ακρόχορδον (akrochordon) = "a wart," in allusion to the appearance of its form of aggregation.

IMA status : Valid species (Pre-IMA 1922) Grandfathered
(8th edition) :  
  (42) Hydrated Phosphates Containing Hydroxyl or Halogen
  (42.04) where (AB)5 (XO4)2 Zq · x(H2O)
  (42.04.01) Akrochordite Group
(10th edition) :
  (08) Phosphates, Arsenates, Vanadates
  (08.D) Phosphates, etc
  (08.DD) With only medium-sized cations, (OH, etc.):RO4= 2:1
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 5.682 Å, b = 17.627 Å, c = 6.832 Å, b = 99.49°
Crystal Habit: Crystals minute, prismatic to lath-like, in spherical or wart-like aggregates
Color: Reddish brown with yellow tint, light to dark brown, colorless, pale pink
Diaphaneity: Translucent
Luster: Dull
Hardness (Mohs): 3.5
Measured Density: 3.26 g/cm3
Cleavage: 2; {010} perfect and second perpendicular to the first
Tenacity: No data
Geologic Setting: A rare mineral in hausmannite ore from a metamorphosed Fe–Mn orebody (Långban, Sweden); in a metamorphosed stratiform zinc orebody (Sterling Hill, New Jersey, USA).
Mineral Association: Pyrochroite, barite, hausmannite, eveite, brandtite (Långban, Sweden); sarkinite,
chlorophoenicite, carbonates (Sterling Hill, New Jersey, USA)


Akrochordite is found as crystalline acicular masses to 0.5 cm across. Along with the akrochordite are crystals of pyrochroite, calcite (which makes up the bulk of the specimen), and an unknown of tan to beige colour. The rarity and quality of this specimen can not be overstated as all of the other specimens from the original find are in museums.
Origin: Långban, Sweden
Harry von Eckermann Collection
Sample size: 7.5 x 5.5 x 3.2 cm
Photo: John Veevaert, Trinity Mineral Co


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