Schefferite |
Habit
Schefferite is found as isolated crystals in limestone, doubly terminated and sharply
formed but with dull faces, the largest 2.3 inches in diameter. It is grayish brown,
glassy, and transparent. The basal parting is distinct, and the cleavages on the prism and
the clinopinacoid are equally perfect. The habit of the crystals is shown in Figures 75
and 76.
| Figure 75 Crystal of schefferite showing the forms c(001), b(010), a(100), m(110), p(101), s(-111), and o(221). Sterling Hill. |
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Figure 76 Crystal of schefferite showing the forms c(001), b(010), a(100), m(110), z(021), p(101), u(111) and s(111). Sterling Hill. |
Optical properties
Schefferite is optically biaxial and positive. 2V = 60° ±; r > v (weak); Z
/\ c
= 43° ; a
=1.690, b =
1.699, g =
1.721, all ±0.003 (Berman).
Occurrence
The crystals were found, with dodecahedral crystals of franklinite, in coarse
limestone at Sterling Hill. They were not abundant, and the author is indebted
to Mr. T. Lang, the finder, for material for the analysis (no.
2), which show's that the mineral is near zinc schefferite, of which it
was at first thought to be the crystallized form. It contains no zinc, however,
and a rather large content of manganese, which brings it close in composition
to the typical schefferite of Sweden.
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Website
© by Herb Yeates 1997-2006.
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This
page created: August 12, 2006 6:52 PM
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