Quartz

Occurrence
Quartz is an abundant constituent of the pegmatite in all parts of the area. Secondary veins, the main filling of which is quartz—partly compact, partly comby and banded with drusy crystals—were 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.

Figure 24
Acicular crystal of quartz showing the forms r(1011), z(0111), and Y(18.0.18.1). Franklin.

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 (18.0.18.1), 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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