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SPI Supplies Individual Loose Microanalysis Standard Item, Minerals Group, Obsidian (alternate to AS
SPI Supplies Individual Loose Microanalysis Standard Item, Minerals Group, Obsidian (alternate to AS
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SPI Supplies Individual Loose Microanalysis Standard Item, Minerals Group, Obsidian (alternate to AS

Item Number AS1255-AB
Availability Contact for Availability
Price  $207.48

This is a reflected light micrograph of a polished, carbon coated obsidian grain. The identifying etched label, which is a feature of our standards, is invaluable for navigating in an electron beam instrument. Obsidian is a volcanic glass containing the full range of rock-forming elements from hydrogen to iron. Because of its glassy state, the alkali elements Na and K are not tightly bound and may therefore migrate, giving instability in intense electron bombardment. However, the composition has been well established through repeated analysis by classes of students, it is a most useful standard for general use in silicate analysis.

Element Wt % Oxide Wt %
H 0.09 H2O 0.80
O 48.63
F 0.07 F 0.07
Na 3.01 Na2O 4.06
Mg 0.04 MgO 0.07
Al 6.94 Al2O3 13.11
Si 34.56 SiO2 73.94
Cl 0.36 Cl 0.36
K 4.18 K2O 5.04
Ca 0.54 CaO 0.76
Ti 0.06 TiO2 0.10
Mn 0.05 MnO 0.06
Fe 1.34 FeO 1.72


Sum 99.9 Sum 100.1