Andesite

a dark-colored volcanic rock composed essentially of plagioclase feldspar and one or more mafic minerals, as hornblende or biot-te.
historical examples

m. dubois discovered these remains in the island of java in andesite tufa of pliocene or at least early pleistocene age.
the cambridge natural history, vol x., mammalia frank evers beddard

surface eruption of quartz-porphyry, rhyolite, and andesite.
history and comprehensive description of loudoun county, virginia james w. head

they are found mostly as loose crystals in gravel, but are known also in igenous rocks like andesite and lamprophyre.
encyclopaedia britannica, 11th edition, volume 7, slice 4 various

a later series of small diorite or andesite dikes cut the ore bodies.
the economic aspect of geology c. k. leith

the lavas and ashes ejected by these volcanoes consist of liparite, dacite, andesite and basalt.
encyclopaedia britannica, 11th edition, volume 15, slice 2 various

the ochils and other hills of middle scotland largely consist of andesite.
the new gresham encyclopedia. vol. 1 part 2 various

an examination of the stones which fell at fort de france showed them to be of a variety of lava called hornblende and andesite.
complete story of the san francisco horror richard linthic-m

the rocks thus extruded are mainly composed of dark, heavy basic material, such as basalt and andesite.
north america israel c. russell

in the main the lava is an andesite, and is very generally of a porphyritic structure.
mount rainier various

the rock in which the hungarian opals occur is eruptive, and of the kind known as andesite.
birds and nature vol. 11 no. 3 [march 1902] various

noun
a fine-grained tan or grey volcanic rock consisting of plagioclase feldspar, esp andesine, amphibole, and pyroxene
andesite
(ān’dĭ-zīt’)
a gray, fine-grained volcanic rock. andesite consists mainly of sodium-rich plagioclase and one or more mafic minerals such as biot-te, hornblende, or pyroxene. it often contains small, visible crystals (phenocrysts) of plagioclase. it is the fine-grained equivalent of diorite.