. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. 188 SVIHSTIflV i^'Uin h'l' of I'Oh'TO KJiH^ ob$eTV(Mi ill till' ik'h'l tln' >izo of the grain riiiigei^ bciweoii 2 mm, to 5 {in-, 0 em., tlie average Imng ;> mm. With few exee|> the rodiA a,rc coiu posed of gfiiLiis oC equal nmi am] these are tJioruughly iiitergrowri. h .?iom,e, liowever, ihe h«. crystals gr-i wry hirge; a lew have bet:! observed wliicli were () em. leug. Tbi' Iioriihk'iuh'H are dceichMlly pris iriatic, blach and J'resh. The ]iar, (isseiiiial stniei-ure of tliesi
. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. 188 SVIHSTIflV i^'Uin h'l' of I'Oh'TO KJiH^ ob$eTV(Mi ill till' ik'h'l tln' >izo of the grain riiiigei^ bciweoii 2 mm, to 5 {in-, 0 em., tlie average Imng ;> mm. With few exee|> the rodiA a,rc coiu posed of gfiiLiis oC equal nmi am] these are tJioruughly iiitergrowri. h .?iom,e, liowever, ihe h«. crystals gr-i wry hirge; a lew have bet:! observed wliicli were () em. leug. Tbi' Iioriihk'iuh'H are dceichMlly pris iriatic, blach and J'resh. The ]iar, (isseiiiial stniei-ure of tliesi rocks to be seriate lunueoid, and comjjose*! of grains averaging 1 nnn. ii size. Ahont 50 per cent ol' this rock is made up of tat,)utar 1 mm. enhe. TlnnMenilc lUori dral, broadly twirineil (-ryslals ol' andesine. ^lust of tliest^ (:ly altereil to ehkH;it;e and zeolik=- A lew crystals of labradorite, k>ss ol* ortlioelase and many of oligoela- occnr. The hornblende is pale green, subhedral. arul pkH)ehroik>., eiinir inkTStitially and cinniilopliyi'icnJly, ami contains elunlocrysts ol i'eldypar Aronnd tlic borders of the }M>nddendos are large mrmbers of nnignetit' grains. Tlic hornl>leudes h,a\'e very raggYMl bnrd(>rs and tke magnetite occur VYithin the shadowy former Ixn-der of the crystals. A])pare!ddy Ih. iinignctitcs are left as a rcsidnnm after the ilissohdng awa;y of tlu) liee-p blende borders. Idornldcmk; makes n,[) 25 per cent of tlie rock. Ab«n; tlie border of tke hornbheidcs ami occnrring apparently as reeryskdli/:- tkm suhstanecs are tinv angile and ealcite crystals. Magnetite ocenrs i. 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
