m(1010), r(1011), z(0111), s(1121), and Y(188.8.131.52)
Crystals of quartz are rare in the district, and the mineral is found mainly in massive
granular form, as vein quartz or as jasper.
Quartz is an abundant constituent of the pegmatite in all parts of the area. Secondary
veins, the main filling of which is quartzpartly compact, partly comby and banded
with drusy crystalswere seen at all the principal openings on Mine Hill. At the
Parker shaft a small quantity, clearly a product of decomposition, was found in druses
lining cavities in altered rhodonite. Clear glassy crystals with the forms m, r,
z are found in cavities in the Kittatinny limestone about Franklin.
In 1927 quartz of a wholly novel habit was found at Franklin. A specimen collected by
Mr. Bauer and described by Palache (257) shows a vein in ore, whose walls are lined with
rhombohedral crystals of calcite on which are minute plates of hematite. The whole cavity
of the vein is filled with a felted mass of the finest fibers of pale-blue crocidolite,
and lying loose in the felt or slightly attached to a wall by one end are needles of
quartz, colored faintly blue by inclusions of
crocidolite. The needles, which range from minute spicules to slender rods 1.2 inches
long and 0.12 inch in diameter, are of trigonal cross section and are extremely steep
rhombohedrons, doubly terminated. They have no visible prism faces and hence are much more
like calcite forms than any other crystals of quartz known to the author. The tips of some
are needle-sharp, and others are terminated by faces of the positive and negative
rhombohedrons, as shown in figure 24.
Acicular crystal of quartz showing the forms r(1011), z(0111), and Y(184.108.40.206).
Although the crystal planes are dull and there are no visible
prism faces, faint reflections were observed at 90°, the prism position, doubtless caused
by minute striations. Readings were obtained from the rhombohedron faces only by wetting
them with alcohol or by attaching glass slips with a film of liquid. The average reading
obtained was r = 87° 80', which agrees most nearly with the form Y (220.127.116.11), r
= 87° 29'. It might, however, almost equally well be that for the form W(0.17.17.1), r =
87° 21'. In the lack of evidence as to whether the form is positive or negative it was
taken as Y and is so drawn in figure 24.
A silicified hematite or jasper of dull-red color was found
occasionally in the Buckwheat mine. Amethyst, chalcedony, and agate, whose names appear in
the older lists, were not confirmed by any specimens examined.
At Sterling Hill quartz appears to be of rare occurrence
except in the pegmatite. A few milk-white crystals of the common form were seen, which
came from the stripping of the calamine deposit and were obtained during the washing of
the calamine, but they are said to have been great rarities.
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