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Ternary diagrams are used to plot three dependent variables that always add up to a fixed value.
They are, for example, commonly used to visualize the compositional variations of rocks or minerals.
A: Comparison of a ternary diagram with a Cartesian coordinate system.
A ternary diagram is a triangular coordinate system; the edges of the triangle are the axes.
B: The three corners of the triangle represent the maximum value of the three variables, in the case of composition that is 100%. By superposition of the three diagrams one gets a triangular coordinate system.
C: How to plot the composition of a rock made of three components (20% + 48% + 32% = 100%) into a ternary diagram.
D: Example application: Compositional variation observed in natural feldspars from volcanic rocks, plotted into a ternary diagram with the end members albite, anorthite and K-feldspar. Axes in Mole-%.