. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. IT f<€lE:sriFIt' MHiVJ-]Y OF PORTO lll€0 • ]n:i'<vi\\. Iiitroihioed zeolites, aim pi'<"<loiiiiji^-iiiiiierals, present, Iiitroihioed Kcolites, epiJotc. iuitij iiJid .|i!iii1z an; iViMpicii! ly TJk; ii'lash}- ol" rlie aiigili! tu'ciir only as of luffs and volcanic bri'ceiiiH. In thcsi>. tlic ' is diMjidcdly porpliy- ritic. Dark brown glass fVrnns 70 per (XHit of tlie rock, which froirtirins ol)undant vesicles and crystallitcs niid sh
. Scientific survey of Porto Rico and the Virgin Islands. Scientific expeditions. IT f<€lE:sriFIt' MHiVJ-]Y OF PORTO lll€0 • ]n:i'<vi\\. Iiitroihioed zeolites, aim pi'<"<loiiiiji^-iiiiiierals, present, Iiitroihioed Kcolites, epiJotc. iuitij iiJid .|i!iii1z an; iViMpicii! ly TJk; ii'lash}- ol" rlie aiigili! tu'ciir only as of luffs and volcanic bri'ceiiiH. In thcsi>. tlic ' is diMjidcdly porpliy- ritic. Dark brown glass fVrnns 70 per (XHit of tlie rock, which froirtirins ol)undant vesicles and crystallitcs niid shows a well-ileYelopcd^ Ihnv strnc- tnj-e. Tlie feldspars lu'rin 10 per cent of rock and tire ial/ular twiniHMi. clear and are of llie olio;(.claHe^»ndesitie variety. Angite up to 15 per (*ent occiirK in small enhedral |.tale green, fractured fresh u:r;nns. Apatite and titanite also oeeiir. fjeneoxene and chlorite arc de~. velopcil in small aniuunts. These pafog-anites or tiugite anjh-sife vitro- |)h}Tes caj]ni)t he ollnn* ihan tlie furiner glassy scnni I'ormed on the sur- Incc «d: some lava'dlUerl ci^iter (Fig. 2i). (Jlitinc Andesitic rucks eontaiiujig olivine are not nhww- dant, tliough several notaldi^' oceiirrcnees of rliem wqtc ohsorvcd. ^JdnJ-' ncnih of La Tjapa. is a large exposure oceujiyiiig the Ited <d' tlie E;io de h Laf)a lor half: a jrulc and^ in ihe vicinity <d' a, volcanic ceiitc'r cast of liapa they arc common as dikes and liicy occur tlirmighoiit the central and western lialf of the distidet as dikes, sills, flows, or as fragments in tutfs and volcanic hn-ccin. The hand spcMnmens of these rocks hiok very much like the aiigUv ; from which ihcv dilTer ordy by the darker colors of lJic gromnt^^. 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 wor
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectscienti, bookyear1919
