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BOSTONITE , in See also:petrology, a See also:fine-grained, See also:pale-coloured, See also:grey or pinkish See also:rock, which consists essentially of See also:alkali-See also:felspar (See also:orthoclase, microperthite, &c.) . Some of them contain a small amount of interstitial See also:quartz (quartz-bostonites); others have a small percentage of See also:lime, which occasions the presence of a See also:plagioclase felspar (maenite, gauteite, lime-bostonite) . Other minerals, except See also:apatite, See also:zircon and See also:magnetite, are typically absent . They have very much the same See also:composition as the trachytes; and many rocks of this See also:series have been grouped with these or with the orthop,hyres . Typically they occur as dikes or as thin sills, often in association with See also:nepheline-See also:syenite; and they seem to See also:bear a complementary relationship to certain types of lamprophyre, such as camptonite and monchiquite . Though nowhere very See also:common they have a wide See also:distribution, being known from See also:Scotland, See also:Wales, See also:Massachusetts, See also:Montreal, See also:Portugal, Bohemia, &c . The lindoites and quartz-lindoites of See also:Norway are closely allied to the bostonites . |
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[back] THOMAS BOSTON (1676-1732) |
[next] CHRISTOFFER JACOB BOSTROM (1797-1866) |
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