|The key to identifying rocks is careful examination. Sherlock Holmes is famous for his amazing deductions, but his real gift was his ability to observe small but critical details. To identify rocks, you must not be shy about taking a hand lens to carefully examine a rock before announcing its identity. Even experienced geologists presented with a simple-looking rock will examine it closely before identifying it.
Igneous rocks are classified according to their texture and composition. Composition refers to both the types of minerals within a rock and the overall chemical makeup of the rock (the two are obviously related). Texture refers to the size and arrangement of the minerals or grains that make up a rock.