Sample: Snyder_1959_8

Sample ID:	Snyder_1959_8 ^[1]
Station ID:	Snyder_1959_8
AT Num:
Volcano:	Little Sitkin
Possible source:
Eruption:
Collector:	Snyder, G. L.
Date sampled:
Sample type 1:	Lava
Color:	dark gray
Final unit:
Text Description:	Low-silica dacite of Little Sitkin dacite. Color: dark gray (N 3). Texture: hypocrystalline, porphyritic with prominent feldspar phenocrysts as much as 6 mm long. Plagioclase, 20-25 percent, ranges from An36 to An62 in individual zoned phenocrysts and between different crystals; average composition is about An50; graphic fritting texture and two-fluid inclusions present in centers or selected zones of some feldspar crystals. Clinopyroxene, 6 percent, appears as reaction rims on some orthopyroxene, 5 percent, and olivine, 1 percent. Accessory: magnetite, 1-2 percent. Groundmass is clear brown glass choked with plagioclase (average composition, An43) and acicular orthopyroxene(?) microlites. Index of refraction of an artificial glass of the powdered rock is greater than 1.540.
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.

full-text PDF 2 MB

plate 23 PDF 7 MB