English: Simplified schematic representation of a metamorphic reaction. Boxes represent the whole rock mineralogy. In this example the reaction is complete: no relict minerals remain. The reaction in question will in nature take place when a rock goes from amphibolite to greenschist facies. Abbreviations of minerals: act = actonolite; chl = chlorite; ep = epidot; gt = garnet; hbl = hornblende; plag = plagioclase. Two non-participating minerals are present in the rocks: these could be (for example) K-feldspar and quartz.