This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1876 edition. Excerpt: ...except very rare, minute laminae of biotite. The feldspars are beautifully built up zonally, with excellent zonal inclosure-lines of half-glassy grains. The groundmass is nearly colorless or very light gray, finely microlitic and granular-feldspathic, containing but little ferrite and opacite. Some titanite is ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1876 edition. Excerpt: ...except very rare, minute laminae of biotite. The feldspars are beautifully built up zonally, with excellent zonal inclosure-lines of half-glassy grains. The groundmass is nearly colorless or very light gray, finely microlitic and granular-feldspathic, containing but little ferrite and opacite. Some titanite is also met with. Another variety, from the River Range, near Susan Creek, Nevada 300, is a somewhat earthy, pale-reddish, and domite-like trachyte, and presents macroscopically some feldspar and biotite. This rather remarkable rock possesses a light, globulitic, glassy base, in which numerous feldspar ledges almost wholly devoid of striation, and subtil, half-transparent grains or needles of a brown and brownish-red color, are disseminated. There is no microscopical biotite, hornblende, augite, or apatite. Nevertheless, there occur, appearing even macroscopically in the sections, granular aggregations of pale, rose-red, isotrope garnet, in seemingly broken grains, free from any interposition, and resembling in all respects the garnets in the Saxon granulites, which, as members of the old crystalline schist series, are doubtless of a different geological origin from these Tertiary eruptive trachytes. Only in one other case has garnet been observed as an accessory ingredient of trachytes, namely, in the Castle Rock from the island of Ischia in Italy.1 Rarely but evenly disseminated through the groundmass, are some sharp grains which in color are an azure or Prussian blue, measure only 0.0025mm, sometimes possess a distinct hexagonal shape, and in all probability belong to haiiyne: they perfectly resemble those microscopical blue crystals which are found well preserved in the sanidins and highly altered in the ground-mass of the trachyte from...
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