How to Spot a Fake Rock

Inspect rocks found outdoors.

Large and small rocks cover the outdoors, from mountains to gardens. Some rocks, such as agates, are tumbled and smoothed for jewelry, while large sedimentary rocks are placed in front of houses as outdoor decor. Often, fake rocks are made to appear real with paints and molds. To spot a fake rock, look at the features of the rock. Place the rock against light sources, such as the sun, to closely inspect the surface and determine if the rock is real or fake.

Things You'll Need

• Lamp

Instructions

1. Hold the rock up to a bright light source, such as a lamp, and take note of any speckles or cracks on the rock's surface. Real rocks have a smooth or bumpy exterior, and may appear to have crystals on the surface when moved around. Fake rocks are very shiny or non-reflective, depending on the type of glaze or paint used on the surface. Real coal or obsidian may also appear shiny. Look for streaks of paint on fake rocks.

2. Feel the rock. Run your fingers across the surface. Most fake rocks will be smooth to the touch, all around the rock. Real rocks have an uneven surface that can be felt when touched. Smooth rocks that formed near water, have light bumps and ridges that you can feel.

3. Take note of the rock's texture, while looking at the rock and feeling with your fingers. Most fake rocks have a smooth finish on the surface with painted ridges and speckles, similar to those on an orange, which are created in the cast. Real rocks have small indentations on the surface that very in size, or irregular holes through the rock's surface.

4. Notice the weight of the rock. Fake rocks, made of materials such as clay, plastic or rubber, are much lighter than a real rock. Real rocks are made of minerals such as silicates, and sediments such as sand, making them dense and heavy.

5. Tap the rock against a hard surface, such as a kitchen counter or patio floor, and listen to the sound the rock makes against the surface. A real rock makes a sharp, medium-to-high pitch sound, depending on the size and weight of the rock. Fake rocks create a low, flat sound that is sometimes hollow depending on the material used to make the rock.

References

• Geo Society: Real Fake Rocks
• Math Science Nucleus: Recognizing Rock Characteristics

Resources

• Geology: Sedimentary Rocks