I've compiled a number of geochemical plotting programs on a website called Geochemical Plotting Programs, and these include a number of Ternary Plotting programs. These are posted on the Teaching Petrology site: http://serc.carleton.edu/NAGTWorkshops/ ... grams.html
For the record, with pyroxenes you don't technically use the full triangle--it's actually cut off at the middle where Fe/Mg=Ca, forming a trapezoid. The mineral stops being a pyroxene when the Ca exceeds Fe/Mg and starts being a pyroxenoid with a rather different crystal structure (wollastonite). A different example might be the three feldspar end-members, though only a sliver of the triangle is actually occupied since K generally refuses to substitute for Ca.
Post subject: Re: Ternary plots: Explained with downloads
Posted: Thu Oct 24, 2013 8:47 pm
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Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
I was thinking the same thing. For us, the feldspar group, or the garnet group would have been a better example.....but now, if we ever need a ternary plot, we know where to find it.
The garnet group would be pretty exciting, though you'd probably need one heck of a polygon to represent it.
If I remember correctly, Dr. Hanneman's Naming Garnets book has a nice cardboard cut-out that does just this, forming into a tetrahedron to display the different chemistries between pyrope, spessartine, almandine, etc. garnets.
It's an interesting read, though I freely admit that much of it went over my head.
You can purchase it by pinging Dr. Hanneman
-Allan
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