Stilpnomelane

Stilpnomelane found at Blanchard Hill (south of Bellingham, WA)

WHAT IS IT?

  • A phyllosilicate mineral having the formula K(Fe++,Mg,Fe+++)8(Si,Al)12(O,OH)27•n(H2O).

  • Phyllosilicates, also known as "sheet silicates", form parallel sheets of silicate tetrahedra with Si205

  • All phyllosilicates are hydrated — contain water or hydroxyl groups.

  • Often looks like biotite

  • Contains banded iron or iron floret formations

  • Hardness: approximately 4

HISTORY

  • Named in 1827 by Ernest Friderich Glocke using the Greek words stilpnos (shining) and melanos (black)

  • First discovered in Moravia, now part of the Czech Republic

WHAT TYPES ARE THERE?

  • Colors: red, dark reddish brown, dark green, brown, golden brown, black

  • Related minerals in the Stilpnomelane Group include:

    • Chalcocite - Cu2S

    • Franklinphilite - K(Mn)(Si,Al)(O,OH)•n(HO) (with n~6)

    • Lennilenapeite - K6-7(Mg,Mn,Fe++,Fe+++,Zn)48(Si,Al)72(O,OH)216•16(H2O)

    • Parsettensite - K2Mn8(Si,Al)12O26(OH)1

WHERE IS IT FOUND?

  • Stipnomenlane is fairly rare

  • Found in the Czech Republic, New Zealand, & U.S. (Blanchard Hill, WA; Antwerp, NY; Saint Peters, PA; Western VT; Minnesota-Michigan iron range)

  • Collection sites in Washington State:

    • Blanchard Hill (south of Bellingham)

    • Alger

WHAT IS IT USED FOR?

  • Rock collecting

  • Jewelry