Mineral Information and Data:

Amarantite
Fe3+2O(SO4)2(H2O)4 • 3H2O [CNMNC approved formula]

Named from the Greek for amaranth, an imaginary purplish red undying flower, for its color.

IMA status : Valid species (Pre-IMA 1888) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
31.09.03.01  
  (31) Hydrated Sulfates Containing Hydroxyl or Halogen
  (31.09) where (A+ B++) (XO4) Zq · x(H2O)
  (31.09.03)
  
Nickel-Strunz
(10th edition) :
07.DB.30
  (07) Sulfates (selenates, tellurates, chromates, molybdates, wolframates)
  (07.D) Sulfates (selenates, etc.) with additional anions, with H2O
  (07.DB) With only medium-sized cations; insular octahedra and finite units
  
Crystal system: Triclinic System
Point group (H-M): 1 — pinacoidal
Unit cell: a = 8.9 Å, b = 11.56 Å, c = 6.64 Å, a = 95.635°, b = 90.985°, g = 97.625°
Crystal Habit: Crystals short to long prismatic; somewhat flattened to nearly square cross-section; usually columnar or bladed masses
  
Color: Red, orangish red to brownish red
Diaphaneity: Transparent
Luster: Vitreous
Hardness (Mohs): 2.5
Measured Density: 2.23 g/cm3
Cleavage: 2; [010], [100] perfect
Tenacity: Brittle
Streak: Yellow
  
Geologic Setting: A secondary mineral formed especially in arid climates.
Mineral Association: Hohmannite, fibroferrite, chalcanthite, copiapite, coquimbite, sideronatrite
  
Other Properties: H2O Soluble.
Comments: Decomposes in H2O, leaving an
insoluble residue.

 

Amarantite
Origin: Chuquicamata, Antofagasta, Chile
Sample size: 4 x 3.5 x 3 cm
Photo: Tom Loomis

 

Amarantite
(zoom-in of above)

 

Amarantite
Origin: Quetena mine, Calama, El Loa Province, Antofagasta, Chile
Sample size: 4 x 4 x 3 cm
Photo: Tom Loomis

 

Amarantite
(zoom-in of above)

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