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| 1. Igneous: these are rocks that solidified directly from molten silicates, which geologists call magma. Examples are: granite, basalt, pumice and flint (which is a form of quartz). |
| 2. Sedimentary: these are formed when igneous rocks are eroded as a sediment under the sea. Fossils are often found in this layer. Examples are limestone, chalk, sandstone. |
| 3. Metamorphic: these are made up of igneous and sedimentary rocks of all ages which have been subjected to intense pressure. Examples are: slate, marble, quartzite. |
