Stilpnomelan

German name.

Structural context

Stilpnomelane
Crystal System triclinicCrystal Class pinacoidalSpace Group P-1

Chemical context

Stoichiometric formulas

Stilpnomelan
mindat.org
  • March 13, 2023(K,Ca,Na)(Fe,Mg,Al)8(Si,Al)12(O,OH)36·nH2O
Stilpnomelane
mindat.org
  • March 13, 2023(K,Ca,Na)(Fe,Mg,Al)8(Si,Al)12(O,OH)36·nH2OThe ratio of ferric vs. ferrous iron varies greatly. An ideal end-member "ferrostilpnomelane" can be represented by K5Fe482+(Si63Al9)O165(OH)48.12H2O. An ideal end-member "ferristilpnomelane" (which is thought to result from oxidation after primary crystallization) can be represented by K5Fe483+(Si63Al9)O216.36H2O. Note that neither end-member composition has been reported yet.
IMA
  • March 13, 2023(K,Ca,Na)(Fe,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
mineralogy.rocks
  • Aug. 30, 2022(K,Ca,Na)(Fe2+,Mg,Al,Fe3+)8(Si,Al)12(O,OH)36·nH2O

Physical properties

ColorColor entities, recognized using a custom trained NER model
    • dark reddish brown
    • golden brown
      • dark green
      Color noteOriginal color note from the source
      Red, brown, black, dark green, dark reddish brown, golden brown
      StreakStreak entities, recognized using a custom trained NER model
          Streak noteOriginal streak note from the source
          White, grey
          Lustre
          Sub-Vitreous
          Pearly
          Sub-Metallic
          Fracture
          Micaceous
          Transparency
          Translucent
          Hardness
          3—4
          Measured density
          2.59—2.96
          Calculated density
          2.667