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.
<a href="//commons.wikimedia.org/wiki/User:Woudloper" title="User:Woudloper">Woudloper</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>