Minerals are the building blocks of rocks and are naturally occuring crystalline solids. On the inside of them their atoms are arranged in an orderly, repeating 3D arrangement. If a material has no orderly arrangement (ex=glassy or amorphous) it is not a mineral! Also minerals are generally inorganic, which mean they don't have carbon. Rocks on the other hand are composed of one or more minerals, and are classified by how they form. If the specimen appears like it has many layers of differing substances in it it is most likely not a mineral, but rather a sedimentary rock. Many sedimentary rocks form from rock fragments (sediments), plant or animal remains being compacted together or through the precipitation of minerals from a solution. If the specimen has a fossil in it it is most likely a sedimentary rock. Also if it has many pebbles in it may be a conglomerate rock. Another type of rock is igneous, which forms when molten rock (magma) cools and solidifies, these rocks sometimes come from the eruption of volcanoes. Igneous rocks typically have tiny crystals through out them. Igneous rocks can come in a variation of colors, from light to dark. Also if the substance looks kind of frothy, and a bit like coral it may be a type of igneous rock known as vesicular extrusive. The last type of rock is known as metamorphic, which forms when igneous, sedimentary or other metamorphic rocks change by heat or pressure. In metamorphic rocks the minerals are changing composition. Metamorphic rocks are classified by their texture and whether you can see bands on the rock. If the specimen does appear to have banding on it (which is different from the layering look of sedimentary rocks) it may be metamorphic.
Many a time the color of a specimen can be very misleading. The color of either a mineral or rock can change from sample to sample. So when identifying a specimen as either a mineral or rock don't rely specifically on the color of it. Also, both rocks and minerals can have crystals in them, its not only minerals that do. When identifying a sample look for the specific characteristics of rocks such as banding, layering or organic elements (fossils). Also look for specific characteristics of minerals such as their luster, is the specimen transparent?
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