6.6 Putting It All Together: Identifying Metamorphic Rocks
Identifying Metamorphic Rocks
You already learned about the basic types of metamorphic rocks and their identifying properties in the Knowledge Check, but here is a refresher below! Keep in mind some of the properties that you have already identified in the photos of rocks when reading these descriptions–they will help you determine the name of each metamorphic rock!
Gneiss: High-grade rock of any composition in which minerals are highly segregated into dark and light layers. The foliation is defined by black and white banding.
Schist: A medium- to high-grade rock with strong foliation that is usually defined by large mica flakes. Other minerals such as garnet can occur in schist.
Phyllite: A low-grade rock that has been recrystallized to have foliated planes of mica or chlorite. This rock usually has a silky sheen caused by the reflection of the light and the alignment of platy minerals.
Slate: A low-grade rock of metamorphosed shale or mudstone that is composed of aligned flakes of clay. Demonstrates foliation.
Marble: A crystalline rock composed of mostly calcite or dolomite, and as a result, it sometimes fizzes when it comes into contact with acid. Commonly non-foliated.
Quartzite: A non-foliated rock composed of quartz or chert.
Let’s Review!
In the exercise below, identify the metamorphic rocks.
