Allright... here goes.

There are several things that can help you tell if a rock you find is a meteorite.

Appearance. Iron meteorites have irregular, angled shapes. Meteorites have a thin dark crust, known as a "fusion crust". This comes from the heating the meteorite experienced as it entered the atmosphere. If the meteorite fell recently, it will be dark in color or black. If old it may be rusty. Soil may also stain old meteorites brown. They come in many shapes and sizes but are seldom symmetrically round.

Texture. Meteorites are solid, not porous. The edges are smooth, dull, and gently curved rather than sharp. The surface may have markings resembling oval thumb prints. It may also be pitted or have tiny bubbles on the surface due to its heating as it entered the atmosphere.

Composition. Many meteorites contain a large precentage of Iron. Tie a string to a magnet and suspend it next to the rock. If it is attracted, Iron is present. Try grinding the rock with a file. Using a hand lens, look for specks of metal.

Density. Assuming this is an Iron meteorite, it will be denser than most rocks of an equal size. Try checking the specific gravity of the suspected meteorite against that of another rock from the area. Specific Gravity is the ratio of mass of the object versus the mass of an equal volume of water. (Mass of rock / Mass of water) How do you find the volume of water? You take a beaker to the brim with water. Put a small cup under the beaker's lip and submerge the rock. Catch the water that pours out with the cup. Weigh the rock, and weigh the water. (Subtract the weight of the little cup from whatever value you get from the cup of water. I should have mentioned weighing the cup earlier- how silly of me!) Divide the weight of the rock by the weight of the water. The result is the specific gravity of our rock. Most Earth Rocks have a specific gravity of 3.3 or less. Most metorites have a specific gravity that is higher than this.


Now the key to each of these attributes is the word "most". There's stuff that doesn't meet some of these criteria that is meteoric in nature and conversely there are non-meteors that do. If you really want to be sure you could try bringing your rock to someone knowlegeable. If you're in college a professor is a great idea, not only because he/she will probably be able to find out, but also because this is an excellent way to be a brown-noser.

I owe most of the info here to a book called "Space and Astronomy Science Fair Projects", by Robert L. Bonnet and G. Daniel Keen. (I made up the brown-noser part.) Make of it what you will.