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SAMPLE INFO : 54-B-12
Sample ID:54-B-12
Station ID:54-B-12
Latitude:53.88707
Longitude:-166.93202
Datum:NAD83
Date Sampled:1954-01-01
Sample Type 1:Lava
Sample Type 2:Dike
Field Lithology:Basalt
Text Description:
feldspathic basalt porphyry from a dike in the Unalaska formation near Summer Bay in Unalaska Bay. It is dark bluish gray and contains phenocrysts as large as 1 millimeter. Phenocrysts compose 10 percent of the rock: 9 percent calcic labradorite, which forms embayed crystals, euhedral laths, and grains with inconspicuous normal zoning ; 1 percent augite (?) , which forms altered euhedra and is replaced by penninite(?) ; and a trace of pyrite. The groundmass has a felty texture and consists of abundant euhedral and subhedral laths of calcic andesine and scattered granules of a black opaque mineral. Alteration is moderate, producing disseminated calcite and penninite and traces of uralite and chlorite.

References:
Geology of Unalaska Island and adjacent insular shelf, Aleutian Islands, Alaska

GEOCHEM DATA