Integrating Research and Education > Teaching Phase Equilibria > Different Kinds of Reactions
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Different Kinds of Reactions

Dave Hirsch, Western Washington University

Examples of phase diagrams and reactions in jpg, pdf and animated-pdf format are available.
A 5 page summary (Acrobat (PDF) 158kB Aug1 07) of this information is available, which can be used as a class handout.

Reactions among solid and fluid phases can be categorized in several different ways, based on what the reaction does, how the reaction progresses, or based on the nature of phases involved.

Categorization based on reaction effect

Categorization based on reaction progress

Categorization based on phases involved

Kyanite inclusions (three tabular grains showing good cleavage and brown-pink interference colors) in andalusite (dark gray interference color, poorly developed cleavage) in a kyanite-andalusite-sillimanite (+ staurolite) quartz vein. This rock was "caught in the act" as kyanite reacted to form andalusite. The photo is from Donna Whitney. This sample is from Hamadan, Iran, and is discussed by Sepahi et al. (2004, J. Metam. Geology 22, 119-134).
Phase diagram for the Al2SiO5 polymorphs. The arrows show that kyanite will react to form sillimanite with increasing temperature or with decreasing pressure. Although not labeled, the pink triangular field at the bottom is the stability field for andalusite. This figure is from Donna Whitney.

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