Image from page 548 of "The American journal of science" (1880)
Title: The American journal of science
Publisher: New Haven : J. D. & E. S. Dana
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library
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from Krageroe, Norway. 511 which at times exhibits slight alteration to leucoxene, is associated with the rutile. A single small grain of pyrite was observed inclosed in one of rutile. Apparently the rutile does not show predilection for one rock mineral more than for another. It occurs entirely enveloped by feldspar, along the sutures of feldspar individuals and of feldspar and quartz, and sometimes penetrates into the substance of both. The rela- tions of the rutile to the silicate rock minerals suggest that it crystallized from the magma as did the feldspar and quartz, Fig. 1.
Text Appearing After Image:
Fig. 1. Microphotograph of kragerite, a rutile-bearing aplite, from Krageroe, Norway. The black grains and crystals are rutile; other con- stituent is chiefly sodic feldspar. Nicols crossed. Magnified 27 diameters. and that the usual order of crystallization Avas observed. These relations are shown in fig. 1, a microphotograph of a thin section of the rock. A thin section of the rutile-rich portion of the rock, repre- senting probably the schlieren of Professor Brogger, was studied microscopically. It was composed chiefly of rutile, together with some biotite, partly altered to chlorite, a few anhedral grains of apatite, and an altered light-colored silicate mineral, probably a potash feldspar. In reflected light the rutile is dark brown to gray with the faintest greenish tinge; in transmitted light it is pleochroic,
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