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. 1896 Excerpt: ...this group of acid effusive rocks, characterized mincralogically by the presence ol basic plagioclase, as well as orthoclase, with occasional quartz, and chemically by high silica and alkalies and (for the acidity) high lime, and low alumina, may be called toscanite. It may be mentioned that they also resemble certain ...
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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. 1896 Excerpt: ...this group of acid effusive rocks, characterized mincralogically by the presence ol basic plagioclase, as well as orthoclase, with occasional quartz, and chemically by high silica and alkalies and (for the acidity) high lime, and low alumina, may be called toscanite. It may be mentioned that they also resemble certain rhyolites from Ponza and from the Euganean hills near Padua. They thus occupy the place in Brogger's4 table filled by the group of quartz-trachyteandesites, and in some cases are so acid as to fall in with his dellensite (dacite-liparite). They approach this especially in their low alumina. Analyses of typical toscanites will be found in Table I. The rock of Monte Calyario is verv much decomposed, so much so that good fresh specimens are difficult to find. I finally obtained some which are quite, though not entirely, fresh at a quarry on the southeast side where work was going on. The rock is rather coarse-grained and resembles many of the porphyries of our western states. The groundmass is light grav, and glassy feldspar phenocrysts abound, which are colored light yellow by the infiltration of ferruginous water. They are chiefly of sanidine with a smaller quantity of acid labradorite. Some 'W1ll1ams, New. Jal1r. IS. Bd. V, 381, 1S85. 2vom Rath, Zeit. d. d. geol. Ges. XVIII, 039, 1S66. Also Dalmer, Ncu. Jahr. 1887, II, 206. 3 Matteucc1, Boll. Com. Geol. Ital. 1890, 284 ff., and Boll. Soc. Geol. Ital. X, 670 ff., 1891. Brouger, Kruptionsfolge bei I'rcdazzo, Kristiania, 1895, 00' quartz grains are present. Biotite flakes are not rare, though these and the augite phenocrysts have suffered much through weathering, being represented by brown limonitic spots in some of the specimens. Some large enclosures of a darker, finegrained, vesicular rock wer...
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Add this copy of Pamphlets. Lettered to cart. $37.63, good condition, Sold by Bonita rated 4.0 out of 5 stars, ships from Newport Coast, CA, UNITED STATES, published 2018 by Palala Press.
