Sample: Snyder_1959_9

Sample ID:	Snyder_1959_9 ^[1]
Station ID:	Snyder_1959_9
AT Num:
Volcano:	Little Sitkin
Possible source:
Eruption:
Collector:	Snyder, G. L.
Date sampled:
Sample type 1:	Lava
Color:	light brownish gray
Final unit:
Text Description:	Low-silica dacite of the Patterson Point formation. Color: light brownish gray (5 YR 6/1). Texture: hypocrystalline, vesicular with "hairy" pumice developed locally, porphyritic with pyroxene and feldspar phenocrysts as much as 3 mm long. Plagioclase, 25-30 percent, varies from An43 to An70 and has an average composition of An51; subgraphic areas of brownish glass and two-fluid negative crystals are included within the plagioclase. Clinopyroxene, 5 percent, and orthopyroxene, 4 percent, in part form agglomerations with magnetite-ilmenite, 1 percent. Groundmass consists of clear pink to brown glass (N=1.506) containing many small gas bubbles.
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