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Sample: Snyder_1959_4

Sample ID: Snyder_1959_4 [1]
Station ID: Snyder_1959_4
AT Num:
Volcano: Little Sitkin
Possible source:
Eruption:
Collector: Snyder, G. L.
Date sampled:
Sample type 1: Lava
Color: medium light gray
Final unit:
Text Description: Andesite of Williwaw Cove formation. Color: medium light gray (N 6). Texture: holocrystalline, porphyritic with both feldspar and pyroxene phenocrysts as much as 4 mm long. Plagioclase, 45-60 percent, ranges in composition from An45 to An60 and averages An51; complex oscillatory zoning and graphic fritting common within individual plagioclase grains. Subhedral clinopyroxene, 10 percent; euhedral orthopyroxene, 10 percent; and anhedral olivine, 1 percent, characterized by brown stains on some fractures. Anhedral magnetite, 5 percent, particularly abundant. Groundmass consists of mesh of feldspar and pyroxene microlites and magnetite dust. Groundmass plagioclase averages An43.
Sample Location:

References Cited

[1] Geology of Little Sitkin Island, Alaska, 1959

Snyder, G. L., 1959, Geology of Little Sitkin Island, Alaska: in Investigations of Alaskan volcanoes, U.S. Geological Survey Bulletin 1028-H, p. 169-210, 1 plate, scale 1:20,000.