. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. 190 kifUENTIFKJ 8UlfM-]Y OF I'ORTO Rl€i III fill oecnin-oiicos the i*«m%s aro ^f', almoBt lioriililejule diorites. ^^'.. s]>ecimoris were ohscrrvod in lln- v(^»lcanie iuils. Iliuid s|)cciiiieiis sliov grains wliicli may approach I nun.; the avci'agf^! is about 1 imn. exei'pt in a rare occui'rcnce whicli lias a clivitiifuHl grouniJmaHs. The lal)rie is, a> a riilo, hiatal, with large; |)henoer\'st:s of plagioelaso and horiibleiide occur^^ ring ill tlio gi-oiiiulmsiss, whi<jli rnaj ho light or ilark g
. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. 190 kifUENTIFKJ 8UlfM-]Y OF I'ORTO Rl€i III fill oecnin-oiicos the i*«m%s aro ^f', almoBt lioriililejule diorites. ^^'.. s]>ecimoris were ohscrrvod in lln- v(^»lcanie iuils. Iliuid s|)cciiiieiis sliov grains wliicli may approach I nun.; the avci'agf^! is about 1 imn. exei'pt in a rare occui'rcnce whicli lias a clivitiifuHl grouniJmaHs. The lal)rie is, a> a riilo, hiatal, with large; |)henoer\'st:s of plagioelaso and horiibleiide occur^^ ring ill tlio gi-oiiiulmsiss, whi<jli rnaj ho light or ilark green, gray, pal*^ l)hie or dull gi'ay. Tlie plagiocdasc; cryslals aro tabular, j*arely striat-'Nl and somctimoK crossed. Ilje hornblendes hlaek. shiny, and Irigtdv prismatic. Ihider the inieroseope tlio fabric h. nsnaJlv f(?ujul to be Si'riate porphy^^ roid, though a few .may he seriate [MH'phvritie. The larger crystals, conr^ Fig. no. ^MomUeii'ie <ui< S?/ir?. niorily in tJie case of h<o'nt)lende, reaeh 5 iiini. in size and the fcldsp/uv .3 mm. The ciystals of the gronndiiuiss may be so small that the texture is nricrocryptx^crysialliiie, as in the r'asc of one luiirnhlende andesitc wi'i- a divitrified matrix. Idie m<tft. eoinniun textur<j is diabiiKJc. The pheoe^ erysts arc horuhlemles and feldspars. The hornblendes are euhedral O' swbhedraT prismatic, dark gretoi, usually Magnetite amounting h- •• per Cent also frequently occurs sectuKhii-ily as a product of rcorganizaii h; alionf the ragged b(u-ders of the , The ;])ars are of ) ?' oligoclasc-andcsine variety, with the envptiasis on^ the anrlesine. and a'- -"^. 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
