Fossils within a sedimentary rock.
Fossils are beautiful pieces of Earth's history that allow scientists and students to understand the inner workings of our planet and the evolution of life. Finding and collecting fossils is a family fun activity that can teach children about organisms that are no longer living today. Many collectors, amateur and professional, mistakenly collect pseudofossils in their quest to find the real items. Learning to differentiate a fossil from a rock will help you avoid false fossils.
Instructions
1. Use your rock and mineral guide to Identify the rock in which the fossil is encased. Fossils are found in a number of materials, including limestone, coal, shale and sandstone. The composition of the sediment allows the hard part of the animal (bones, shells and teeth) or plant to become compressed. Over time and under great pressure, these animal and plant remains are trapped in layers of sediment where they become fossilized, leaving an imprint on the rock. In metamorphic rocks like marble and slate, the crystallization process will cause the fossil to be consumed and destroyed by natural chemical reactions. Igneous rocks, such as granite and obsidian, are created at such high temperatures that it is impossible for organic material to survive. Sedimentary rock offers your best chance of finding a fossil.
2. Examine the fern-like markings that you find on many rocks. These aren't fossils. They're plant-like patterns called dendrites, which are largely credited with misleading collectors by appearing as plant imprints. Dendrites are caused by a chemical process in the rock and are found in metamorphic rocks. If your rock consists of layered bands of diverse colors, such as slate and gneiss, it is safe to call it metamorphic. If your rock is crystallized by a chemical process, such as marble and quartzite, it is unable to hold a true fossil. The markings you see on these types of rock may be discarded as false fossils.
3. If you're near a university or natural history museum, find out whether a carbon-dating test or an organic test can be performed on your rock specimen to determine its age and composition. Metamorphic and igneous rocks do not contain any carbon or organic material that can be tested. However, a sedimentary rock, such as limestone, will yield a conclusive result. The limestone can then be tapped against a hard surface, like concrete, to break apart the sediment. The fossil, however, will not break apart in various, mismatching pieces like the limestone.
4. Consult your local educational institution or a nearby United States Geological Society center for answers on fossils that you may not find on your own. A geologist or paleontologist will be able to identify the rock and determine whether it holds a true fossil.
Tags: your rock, break apart, chemical process, false fossils, metamorphic rocks
