These tables will help you identify almost any rock you're likely to find. First, decide whether your rock is igneous, sedimentary or metamorphic.
Igneous: A tough, frozen melt with little texture or layering; mostly black, white and/or gray minerals; may look like lava (about igneous rocks)
Sedimentary: Hardened sediment with layers (strata) of sandy or clayey stone; mostly brown to gray; may have fossils and water or wind marks (about sedimentary rocks)
Metamorphic: Tough rock with layers (foliation) of light and dark minerals, often curved; various colors; often glittery from mica (about metamorphic rocks)
Next, check the rock's grain size and hardness. Then start in the left column of the appropriate table below and work your way across. Follow the links to pictures and more information. If you don't find a match, try another of the three big types.
Grain Size: "Coarse" grains are visible to the naked eye (greater than about 0.1 millimeter), and the minerals can usually be identified using a magnifier; "fine" grains are smaller and usually cannot be identified with a magnifier. (using a magnifier, identifying minerals)
Hardness: Hardness (as measured with the Mohs scale) actually refers to minerals rather than rocks, so a rock may be crumbly yet consist of hard minerals. But in simple terms, "hard" rock scratches glass and steel, usually signifying the minerals quartz or feldspar (Mohs hardness 6-7 and up); "soft" rock does not scratch a steel knife but scratches fingernails (Mohs 3-5.5); "very soft" rock does not scratch fingernails (Mohs 1-2). Igneous rocks are usually hard.
| 