Sample: Snyder_1959_1

Sample ID:	Snyder_1959_1 ^[1]
Station ID:	unnamed1
AT Num:
Volcano:	Little Sitkin
Possible source:
Eruption:
Collector:	Snyder, G. L.
Date sampled:
Sample type 1:	Lava
Color:	light reddish gray
Final unit:
Text Description:	Basalt from Williwaw Cove formation. Color: light reddish gray (5R 6/l). Texture: holocrystalline, porphyritic, with large, diameter 15 mm phenocrysts of greenish black augite (5 GY 2/1). Plagioclase phenocrysts, 10-15 percent, range from An45 to An65 in individual and separate crystals and average An57. Augite (nZ: 1.705, nX : 1.676) occurs as remarkably inclusion-free megaphenocrysts and as groundmass dust, making 40 to 45 percent of the rock. Subhedral olivine, 2 percent, and magnetite-ilmenite, 1 percent, are accessory minerals. The groundmass is a microcrystalline aggregate of all the above minerals.
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