Mineral Information and Data:

Aristarainite
Na2Mg[B6O8(OH)4]2 • 4H2O [CNMNC approved formula]

Named for Lorenzo Francisco Aristarain (1926- ), Argentine mineralogist specializing in borate deposits, La Plata University, Buenos Aires, Argentina.

IMA status : Approved Species 1973 (IMA1973-029)
CLASSIFICATION 
Dana
(8th edition) :
26.06.05.01  
  (26) Hydrated Borates Containing Hydroxyl or Halogen
  (26.06)
  (26.06.05)
  
Nickel-Strunz
(10th edition) :
06.FB.05
  (06) Borates
  (06.F) Hexaborates
  (06.FB) Ino-hexaborates
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 18.886 Å, b = 7.521 Å, c = 7.815 Å, b = 97.72°
Crystal Habit: Prismatic well-formed crystals, elongated or tabular; rosette-like aggregates
  
Color: Colorless
Diaphaneity: Transparent
Luster: Vitreous
Hardness (Mohs): 3.5
Measured Density: 2.03 g/cm3
Cleavage: 3; {001} and {100} perfect, {110} fair
Tenacity: Brittle
Fracture: Splintery
Streak: White
  
Geologic Setting: In a playa evaporite sequence (Tincalayu deposit, Argentina); at a desert borax spring (Eagle Borax Spring, California, USA).
Mineral Association: Borax, kernite, rivadavite, ezcurrite, ameghinite, mcallisterite, kurnakovite, searlesite, probertite, ginorite, tincalconite, ulexite, halite, magnesite (Tincalayu deposit, Argentina); thenardite, blodite, mcallisterite, santite, hexahydrite, halite, gypsum (Eagle Borax Spring, California, USA)
  

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