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. 1914 Excerpt: ... we have a series of highly basic compounds commonly free from alkalies. They are morphologically like biotite and are characterized by the presence of the univalent radicle A102R," R" being either Mg, Ca, Fe," or Mn. The most basic mica of the group, the end member of the series, is xanthophyllite, which has ...
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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. 1914 Excerpt: ... we have a series of highly basic compounds commonly free from alkalies. They are morphologically like biotite and are characterized by the presence of the univalent radicle A102R," R" being either Mg, Ca, Fe," or Mn. The most basic mica of the group, the end member of the series, is xanthophyllite, which has approximately the formula Al(Si04)3(A102R")9, with R9 = Mg6Ca3-In seybertite three of the univalent radicles are replaced by hydrogen, and in chloritoid there is still more replacement of a different kind. The ideal formulae are as follows: Xanthophyllite. Seybertite. Chloritoid. ySi04--(A102Ca)3 ySiO--H, Si04=(A102H2)H2 Al--SiO=(A102Mg)3 Al--Si04=(A102R)3 Al--Si04=(A10H)H si04=(A102Mg)3 si04=(A102R)3 si04=(A10, Fe), In xanthophyllite there is always some hydration, and in the other species there are various small replacements of Al by Fe'," of Fe" by Mn, etc., as in all the other micas. Ottrelite, a fourth member of the series, is like chloritoid, but contains Si308 instead of Si04; that is, its formula is trisilicate The pure theoretical compounds have the following composition: Xanthophyllite decomposes on ignition into two portions--one soluble and the other insoluble in hydrochloric acid. The insoluble portion has the composition of spinel, a mineral which generally accompanies clintonite micas, and of which the formation is rendered intelligible by the formulae.1 The actual decomposition may perhaps be represented by the subjoined equation: Xanthophyllite. Spinel. Garnet. Magnesia. CMAl, (Si04)3Ou = 4MgAl204+Al2 (SiQ4)3Ca3 + 2MgO. 1 For a different interpretation of these micas see the former edition of this memoir, U. S. Geol. Survey Bull. 125, 1895; also for details see Clarke and Schneider, TJ. S. Geol. Survey Bull...
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