File:The Quarterly journal of the Geological Society of London (1898) (14799025973).jpg

Identifier: quarterlyjourna541898geol (find matches)
Title: The Quarterly journal of the Geological Society of London
Year: 1845 (1840s)
Authors: Geological Society of London
Subjects: Geology
Publisher: London (etc.)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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is also present a great deal of minute quartz in the granularcondition, the particles interlocking with sinuate contours, forming Thft mimbed Jire those of the slides pr.^jerved in my cabinet. 378 DE. C. CALLAWAY ON THE METAMORPHISM OF (Aug. 1898, aggregates similar to those just noticed. Mixed up with the chloriteaud other interstitial matter, there is a fair proportion of quartz invery small angular fragments. It can hardly be doubted that theminutely granular aggregates consist of small fragments of quartzand a little felspar, which have coalesced under the influence ofheat and pressure; while the angular particles embedded in thematrix are original fragments which have been kept asunder, andprotected by their soft environment. The pressure to which thisrock has been subjected has been comparatively slight. No. 449.—This slide also is very quartzose, and the other con-stituents are similar, except that a little white mica is present, and Pig. 1.—Schist from Pant-y-Glo (No. U9).
Text Appearing After Image:
(A.lteration partial; quartz-fragments conspicuous, some of them tailing cjfiinto mosaic. The minute quartz is often coalescent, Wliite mica (notfragmental) is present in small proportion.) there is less epidote. This rock has been compressed to a moderatedegree, so that a distinct schistosity is produced, and this is stronglyaccentuated by the mica. Many of the larger quartz-fragments arestill quite sharp and angular, lying for the most part with theirlonger axes parallel to the foliation ; but some of them have appa-rently been converted into granular mosaic. A few of them tail offin one direction into mosaic, as if the thinner end of the fragmenthad yielded to the heat, while the main part of it had resisted.Minute particles of quartz surrounded by matrix are still angular. Vol. 54.) GEITS AND SHALES IN NORTHERN ANGLESEY. 379 No. 448.—Alteration greater, and schistosity more stronglymarked. Contortion very intense, some of the micaceous folia beingtwisted and sheared again and ag

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