Characteristics for identifying and classifying types of rock:
Crystals have flat surfaces. The flat surfaces of crystals are shiny and may sparkle.
Geodes appear as round, hollow rocks that contain crystals. Geodes are caused by minerals seeping into cracks between rocks and forming crystals.
Soft and sometimes crumbly rocks that are formed in layers over a long periods of time.
Rock with layers that look like ribbons and may contain crystals. Metamorphic rock is formed below the earth's surface due to heat and pressure.
Igneous rock formed from lava that is cooling quickly is smooth, glasslike, and may contain tiny bubbles. When igneous rock is formed slowly within the earth, the rocks have a coarse mineral texture.