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. 1906 Excerpt: ...applies only to the form and habit and not to the mineral, which is identical with the larger crystals. For this reason, as already PLATE XX. n Brogger, W. C. (Mtrieralien der Syenitpcgmatitgfingc, Zeitsch. fiir Kryst.. p. 164), places pyrite and other sulphides in pegmatite dike veins among the minerals formed at the ...
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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. 1906 Excerpt: ...applies only to the form and habit and not to the mineral, which is identical with the larger crystals. For this reason, as already PLATE XX. n Brogger, W. C. (Mtrieralien der Syenitpcgmatitgfingc, Zeitsch. fiir Kryst.. p. 164), places pyrite and other sulphides in pegmatite dike veins among the minerals formed at the second period of consolidation, when the action of water and other mineralizers was more potent in forming minerals than during the first period of consolidation, which was that of ordinary magmatic solidification. He also (p. 161) notes that while zircon is formed during the first period, it is highly probable that it is iormed by the action of mineralizers, probably fluorine; and it also occurs (p. 164) among the minerals of the second period. A. La Croix (N'ouvelles Archives du Museum, Paris. 1902, Tome 4, p. 86) describes, in an alkaline granite from Madagascar (frequently pegmatitic) allotriomorphic or idiomorphic zircon inclosed in the quartz, sometimes in the feldspar. He regards this zircon as later than all the minerals except quartz. It Is distributed in the granite, and not localized in veins, lie regards it as the product of emanations contemporaneous with the final consolidation of the rock. THIN SECTIONS SHOWING TWO PERIODS OF CRYSTALLIZATION IN ALASKITE. A, Two generations of crystals in alaskite fabric. First generation consists of feldspars largely altered to fine muscovite (partly sericite; s, orthoclase partly altered to fine muscovite (sericite); a, andesineoligoclase partly altered (less than orthoclase) to fine muscovite. Second generation consists of clear unaltered feldspar and quartz; o, fresh orthoclase; m, fresh microcline; q, quartz. Note frequent idiomorphic crystals of first generation (e. g., the two altered orth...
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