Figure 4.08. Na-Al-Si-O Composition Diagram. The chemical compositions of quartz (Qz - SiO2), albite (Ab - NaAlSi3O8), jadeite (Jd - NaAlSi2O6), and nepheline (NaAlSiO4) are shown on a 3D tetrahedral graph of the elements Na-Al-Si-O in atom percent units. Move the slider to see the mineral compositions plotted and the tetrahedral plot rotated. All 4 minerals lie in a plane, as shown by a pale triagle with corners Si-O-NaAlO2. Furthermore, all 4 minerals lie on a line stretching between SiO2 and NaAlO2. Because the minerals all plot along a line, they are in a 2-component system. Any two points along the line could be chosen as the two components.

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