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