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(K,Na,Ca)4(Fe2+,Mg,Mn,Zn)48(Si,Al)72(OH,O)216.nH2O
Triclinic
Ferrostilpnomelane, a potassium ferrous-iron aluminum silicate hydroxide hydrate mineral of the stilpnomelane group, is uncommon locally. Only one occurrence is known. It occurs as massive, blackish, impure, foliated masses surrounding dendrites of rammelsbergite and gersdorffite (Figures 21-35 and 21-36) at Franklin (Oen et al. 1984). It is also associated with barite, calcite, and sphalerite; small amounts of nickeline or fluorite may be present, but are not commonly seen in hand-specimen. A microprobe analysis of this mineral is presented in Table 14. Calculation of cations on the basis of the sum of octahedral and tetrahedral cations = 120, yield Fe = 22.8 and Mg = 20.4 atoms, indicating that this material is near a mid-member in the ferrostilpnomelane-lennilennapeite series.
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| Copyright © 1995 by Pete J. Dunn |
Website
by Herb Yeates
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