. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. ihem haxQ iiieorjMjriitod !«: iiiiioli fragiiicntiil iriattirial that they may he 'ii for tiifl's. The «Iioritos arc imiform in compositJoii and ,t>"ei!era) {ip|)earaiice, and wlien not inoilified hv inchjsioiis are readily recognized in the field (Fj«;. 31). Many of the aiuh'sitic rocks might be mistaken for basalts by tlie casual oh«'rver. hot tyrneal basalts are deeidediv rare. Basic varieties of ande^-. sites whirb havi' l>een called l)a>alts are more t^ommon, but all of these fHoks. fh
. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. ihem haxQ iiieorjMjriitod !«: iiiiioli fragiiicntiil iriattirial that they may he 'ii for tiifl's. The «Iioritos arc imiform in compositJoii and ,t>"ei!era) {ip|)earaiice, and wlien not inoilified hv inchjsioiis are readily recognized in the field (Fj«;. 31). Many of the aiuh'sitic rocks might be mistaken for basalts by tlie casual oh«'rver. hot tyrneal basalts are deeidediv rare. Basic varieties of ande^-. sites whirb havi' l>een called l)a>alts are more t^ommon, but all of these fHoks. ! I»asalri(^ in appearanee. show only the ;' vrtrietie^ of the plagiochise feldspars. At K It, on the fomnrio road, an ainvgda- loidal p<H-phyrifK' TO<-k of basaltic appearance intrudes the tirlTs. It is e»)rHpos(,Hl id* hitb-shafHMl phenoerysts of plagioelase in a dark, basic gronnilniass of ferromag'nesian minerals. 1die vesiiadar cavities liaw' been filled with f|nartz find zeolite. While this ruek bus a typieol basaltic appearance, the pkgioclaso low extinction angles (less (bun 10'^).. 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
