A rock identification key is a system used to identify rocks. It's usually in the form of a chart or table with several common descriptive properties of rocks.
To use a rock identification key, it's important to have an idea of what rock class is being identified. Rock classes include sedimentary, metamorphic or igneous. The rock's texture, grain size and overall pattern is also observed in a rock identification key. If possible, a basic hardiness test should be conducted to help identify what minerals compose the rock. A rock identification key lists all possible combinations of certain rock features, which determines the type of rock being studied.