Metamorphic Rock Classification
Metamorphic rocks come in two main types: foliated and non-foliated. You'll ace identifying them once you know the differences!
Foliated rocks show preferred orientation of minerals. They follow a progression based on increasing pressure and temperature: shale (a sedimentary rock) transforms to slate fine−grained,breaksintosheets, then phyllite fine−grainedwithacrinklytexture, then schist finetocoarse−grained,shinyfrommicas, and finally gneiss coarse−grainedwithdistinctivelightanddarkbands.
Non-foliated rocks don't show this alignment. Quartz sandstone becomes quartzite (hard enough to scratch glass), while limestone transforms into marble (fizzes in acid due to calcite content). These transformations often occur at convergent boundaries where oceanic lithosphere meets continental lithosphere.
Pro Tip: When identifying metamorphic rocks, look for foliation patterns first, then check specific properties like grain size and mineral composition to determine exactly which type you have.