This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1871 edition. Excerpt: ... when viewed in certain directions. They have been supposed to pass into each other by imperceptible degrees, and their chemical composition would seem to favour this view, while the differences of crystalline form are not great enough to forbid the supposition. Dana, however, considers the microscopic ...
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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1871 edition. Excerpt: ... when viewed in certain directions. They have been supposed to pass into each other by imperceptible degrees, and their chemical composition would seem to favour this view, while the differences of crystalline form are not great enough to forbid the supposition. Dana, however, considers the microscopic investigation of the felspars to be entirely in favour of the distinctness of the species. He remarks that oligoclase and orthoclase are often found. together in granite, obsidian, and trachyte, and yet keep themselves distinct, even to microscopic perfection. This has also been shown, by the Rev. Professor Haughton, to be the case with albite and orthoclase in the granites of Cornwall and of Ireland. The chief species, according to Dana, are: --O. ratio Cleavages. for R R.Si. Anorthite... 94 Iff & 85 50" 1.3.4 Labradorite. 93 20 86 40 1.3.6 Hyalophane----1.3.8 Andesite...----1.3.8 Oligoclase... 93 50 86 10 1.3.9 Albite 93 36 86 24 1.3.12 Orthoclase.. 90 00 90 00 1. 3. 12 The amount of silica increases with the increasing proportion of alkalies, from anorthite, which is usually without any alkali, to albite and orthoclase, with the protoxide bases solely alkaline. The following table, from Page's Handbook of Geological Terms, exhibits the range of composition of the chief felspars: --Sil. Alum. Pot. Soda. lime. Iron Ortho. own 15-20 7-14 l-l 1-s 1-2 Albite. 67-71 14-20 1-4 7-11 1-J 0-1 labrad. 4s-50 29-30 0-1 1-4 0-1-2 1-3 A mirth. 42-40 32-37 0-1 0-1 10-18 0-1 Oligo. 60-64 1s-24 1-8 2-10 2-5 0-1 Only albite and orthoclase have, as yet, been found in Cornwall and Devon; these are described under their respective headings. Some of the foreign felspars are valuable as ornamental stones, while the large deposits of kaolin or china clay, ...
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Add this copy of A Handbook to the Minerology of Cornwall and Devon to cart. $73.99, good condition, Sold by Bonita rated 4.0 out of 5 stars, ships from Newport Coast, CA, UNITED STATES, published 2015 by Palala Press.
