| Element | % | | Oxide | % |
| O | 47.08 | | | |
| Na | 3.23 | | Na2O | 4.35 |
| Mg | 0.08 | | MgO | 0.13 |
| Al | 15.10 | | Al2O3 | 28.53 |
| Si | 25.34 | | SiO2 | 54.21 |
| K | 0.34 | | K2O | 0.41 |
| Ca | 8.43 | | CaO | 11.80 |
| Ti | 0.04 | | TiO2 | 0.07 |
| Fe | 0.29 | | FeO | 0.37 |
| Sr | 0.07 | | SrO | 0.08 |
| Ba | 0.01 | | BaO | 0.01 |
|
|
|
| Sum | 100.0 | | Sum | 100.0 |
|
|  | |
| 200 µ m
| |
|
This is a reflected light micrograph of polished, carbon coated
plagioclase felspar crystals.
The identifying etched label, which is a feature
of our standards, is invaluable for navigating in an electron beam instrument.
Felspars are the most abundant group of silicate minerals with compositions
ranging from potassium to sodium to calcium rich end members. The
plagioclases range from sodium rich (albite - #1 in this set) to
calcium rich (anorthite). This example is a labradorite with 65%
of the anorthite end member and is therefore a most useful
standard for general silicate work.
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