The Quarterly journal of the Geological Society of London . estone, arecharacterized by the presence of augite as the chief colouredmineral. (1) Pegmatites. Pegmatites are frequently associated with the granulitic granites,from which they are distinguished by the tendency of minerals ofthe same kind to group themselves together in irregularly-shapedmasses. Quartz, occupying the interior of the mass, is generallycoarsely granulitic in texture, and felspar less so; while, if biotitebe present, it occurs in pockets carrying large strongly-cleavedindividuals, either enclosed within the felspar or
The Quarterly journal of the Geological Society of London . estone, arecharacterized by the presence of augite as the chief colouredmineral. (1) Pegmatites. Pegmatites are frequently associated with the granulitic granites,from which they are distinguished by the tendency of minerals ofthe same kind to group themselves together in irregularly-shapedmasses. Quartz, occupying the interior of the mass, is generallycoarsely granulitic in texture, and felspar less so; while, if biotitebe present, it occurs in pockets carrying large strongly-cleavedindividuals, either enclosed within the felspar or arranged aroundthe periphery of the intrusion, especially in the neighbourhood ofangular terminations (see figs. 8 & 9, p. 69). Between the centralquartz aggregates and the surrounding orthoclase, there is frequentlya narrow granulitic zone composed of quartz and orthoclase inabout the same proportions as in graphic granite. In other cases,a similar zone containing flakes of biotite arranged in haphazardfashion, surrounds the felspar (fig. 10, p. 69)..
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
