. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. IIOIXIH. ilFAilJJUV OF THF CiKl MOAH:AVA UA niHTHIFT jSi rayoy fierics. A iinn\\) of hills easl of (' luriiKMl by a boss of thi^ , the iiuir,triiia,l oi: which is dioritt' and m-sir its ha^^c a dike of iHiirito atidositf and a How of vcsiciihir oljviiio-froc 1m«ilt are found (Fig. M\). \he iwk eonsist^5 of 2 lo .'i Jiiiii. mn^m.^^ of dark .hivoh and occasional ^^pcckn oC or pvroxeno in a wliiu' to light ;!n, fiidd of feldspar, lii sonic varieties tlie qurtrt
. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. IIOIXIH. ilFAilJJUV OF THF CiKl MOAH:AVA UA niHTHIFT jSi rayoy fierics. A iinn\\) of hills easl of (' luriiKMl by a boss of thi^ , the iiuir,triiia,l oi: which is dioritt' and m-sir its ha^^c a dike of iHiirito atidositf and a How of vcsiciihir oljviiio-froc 1m«ilt are found (Fig. M\). \he iwk eonsist^5 of 2 lo .'i Jiiiii. mn^m.^^ of dark .hivoh and occasional ^^pcckn oC or pvroxeno in a wliiu' to light ;!n, fiidd of feldspar, lii sonic varieties tlie qurtrtz is iiof apparent in flii' hand sfiecinien. fn thin section the rock is (MiidgTanidar ami made np fiTains whieli average o mm. in size. OligtM-lasc in dull, tidinhir. snle liedral, twinned crystals amoniits to .">.'» per cent. Some of the oligoelase K twinned aeeonh-ng \u hotli the alhite and ('arlsha<l laws. The Inotite. lo 15 per cent. .Mueli of the hiotite has gone over into the chlorite. The lirsi oecurrenee inentioncd above has .1 ]>er etnit of idear, colorless aiigite, ilie second a small area of green hornblende. In the former tdie rpiariz "fi:»rs in iotcrstiiial material in the latter as mnJtit'orm grains wilh irumy strings (tf inelusi«>ns. In both, (piartz is prcstnd; to ahont 2t) per .^^^^^^^Ah)vkH of this type oe<mr thronghont the older -^"?rics as l)osscs or thick ininisions. They ai'e mi)re common than their '?-er^grained, eqnivalents, tin- hornldcnd<. andesitcs. snggt'stirig a genoth- e iation existing ])etween drij^th and the occurrence of hornblende. As. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original New York Academy of Sciences. New York, : The Academy
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectscienti, bookyear1919
