A rock hammer makes identifying rocks and crystals easier.
Identifying crystals and rocks is a popular hobby and a way to learn more about the natural world. Both are made of minerals. Crystals are a single mineral type that you will need to identify. Rocks are composed of several different minerals. You need to identify the minerals and look at how they are bound together to determine what type of rock it is. With just a few simple tools and a mineral-identification guide, you can begin to learn more about geology.
Instructions
Prepare a Surface
1. Prepare a fresh surface of the rock or crystal. Use a rock hammer to break off a fragment. Note the resulting surfaces that are created in your specimen and the angles between these surfaces. Because of differences in how the atoms are bound together, minerals will reveal different patterns of breakage, forming, for example, cubes, rectangles, or hexagons. If you are observing a crystal you can also observe its overall shape. Some minerals, like halite (table salt) will tend to form cubes; others, like gypsum, will form thin needle shapes.
2. Note the color and luster of the broken surface. The color of minerals is determined by the degree to which light is absorbed or reflected. Both chemical elements and the internal structure of minerals contribute to the color. Luster is a description of the surface appearance of the minerals. Geologists use terms such as metallic, silky, earthy, or vitreous (glasslike) to describe luster.
3. Test the hardness of the exposed crystal or rock surface. Can you scratch it with your fingernail or a knife blade? Can the crystal or rock scratch a piece of glass? If you are examining a rock, can you break off individual minerals, or are they strongly bound together?
4. Feel how heavy the rock or crystal is for its size. It may be light because of the minerals and elements in it. For example, rocks with a lot of iron will feel heavy. It could also feel light because there are air pockets in it. Tuff, made when ash from an erupting volcano hardens, has many air pockets and can feel very light.
5. Look for banding of different colors or minerals in your specimen. This can be especially helpful in identifying different rock types. Sedimentary rocks, like sandstone or limestone, can have horizontal bands that show how the minerals were deposited over time. Metamorphic rocks, like marble, can have wavy bands that form when minerals are deformed by pressure and temperature. Consult a mineral-identification guide to find the name of a crystal or rock type that has the characteristics you have observed.
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