. Bulletin of the British Museum (Natural History), Mineralogy. 66 VOLCANIC ROCKS FROM THE CAPE VERDE ISLANDS Marker (1907: 102) has described the Beagle specimens from S. Tiago and Httle need be added to his account except that in [CD. 4706] from Quail I., Praia, described by him as a fourchite (p. 103), the base is a glass, and analcime is confined to the vesicles. A common type amongst these S. Tiago limburgites is characterized by the 'clotting' of the httle augites of the base into stellate groups and by the skeletal 'fir-tree' growths of the magnetite belonging to this phase of crystalli
. Bulletin of the British Museum (Natural History), Mineralogy. 66 VOLCANIC ROCKS FROM THE CAPE VERDE ISLANDS Marker (1907: 102) has described the Beagle specimens from S. Tiago and Httle need be added to his account except that in [CD. 4706] from Quail I., Praia, described by him as a fourchite (p. 103), the base is a glass, and analcime is confined to the vesicles. A common type amongst these S. Tiago limburgites is characterized by the 'clotting' of the httle augites of the base into stellate groups and by the skeletal 'fir-tree' growths of the magnetite belonging to this phase of crystallization (Fig. 12&). Others show the incoming of feldspar in the base passing into the limburgite- basalts [C. 4713] already described (p. 61).. Fig. 17. Augitite, Bird I., S. Vicente [ 64614] Limburgites also occur among the newer lavas of Fogo, and consist of the usual brown, glassy base crowded with microlites of titanaugite and magnetite and are rich in phenocrysts of titanaugite and olivine up to i mm. in size ([820], R. Joao Pinto, and [836], shore, 1-5 km. south of S. Filipe). An augitite, [ 64614], from the Challenger Collection, labelled 'dyke. Bird I. near St. Vincent, C. Verde Is.', has been recently described by the present author (1946: 241).' Of quite simple mineralogical composition, phenocrysts of brown titanaugite set in a base of pale glass with microlites of similar augite and magnetite grains it is chiefly noteworthy for its unusual texture (Fig. lya). The specimen has a' worm-eaten wood' appearance owing to the numerous very long and narrow parallel vesicles. The black titanaugite phenocrysts are long and narrow and both these features die out towards one end of the specimen suggesting that this is the chilled margin of the dike. The pyroxenes range up to 5 mm. or more in length elongated in ' This specimen was described by A. F. Renard (1889: 17) as 'a somewhat fibrous lava, which may be classed with the Pyroxenites . .' using this name in the se
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