Mineral Information and Data:

Arcanite
K2SO4 [CNMNC approved formula]

Named from the Latin arcanum duplicatum, for double secret, a medieval alchemical name.

IMA status : Valid species (Pre-IMA) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
28.02.01.02  
  (28) Anhydrous Acid and Sulfates
  (28.02) (A+)2 XO4
  (28.02.01)
  
Nickel-Strunz
(10th edition) :
07.AD.05
  (07) Sulfates (selenates, tellurates, chromates, molybdates, wolframates)
  (07.A) Sulfates (selenates, etc.) without Additional Anions, without H2O
  (07.AD) With only large cations
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 5.76 Å, b = 10.05 Å, c = 7.46 Å
Crystal Habit: As thin plates, pseudo-hexagonal from cyclic twinning
Twinning: On {110}, cyclic.
  
Color: Colorless, yellowish
Diaphaneity: Transparent
Luster: Vitreous
Hardness (Mohs): 2
Measured Density: 2.66 g/cm3
Cleavage: 1; {010} and {001} good
Streak: White
  
Polymorphism and Series: Forms a series with mascagnite.
Geologic Setting: In a pine railroad tie (Santa Ana mine, California, USA); in hydrothermally altered rock in a geothermal field (Cesano geothermal field, Italy); derived from bird guano on islands and bat guano in caves.
Mineral Association: Syngenite (Cesano geothermal field, Italy); swaknoite, mundrabillaite, dittmarite (Arnhem Cave, Namibia)
  
Other Properties: H2O Soluble.

 

Arcanite
Origin: Tolbachik Volcano, Kamchatka, Russia
Sample size: micromount
Photo: Diederik Visser

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