Density is how heavy a rock is for its size or compared with other rocks. It's not enough to say your rock is heavy. Unusual density is one of meteorites' more characteristic features. Metal is distributed evenly throughout ordinary chondrites. Stony-iron meteorites have metal and olivine crystals. Iron meteorites are made of dense and compact metal. This is a definitive test of a meteorite, but requires a chemical analysis or acid etching to detect. The metal in a meteorite has the unusual characteristic of containing up to 7% nickel. Stony meteorites contain small flecks of metal that are evenly distributed throughout the meteorite. Stony iron meteorites are about half metal, half crystals of green or orange olivine. Iron meteorites have a dense, silvery appearing interior with no holes or crystals. Meteorites without metal in them are extremely rare and they need to have some of the other characteristics of meteorites to be able to identify them as meteorites. You can see the metal shining on a broken surface. Most meteorites contain at least some iron metal (actually an alloy of iron and nickel). Ordinary chondrites and stony meteorites like the one at left have smooth surfaces or regmaglypts. Most iron meteorites, like the example at right, have well-developed regmaglypts all over their surface. The surface of a meteorite is generally very smooth and featureless, but often has shallow depressions and deep cavities resembling clearly visible thumbprints in wet clay or Play-Doh. This web page has some good examples of desert varnish. Usually, but not always, you will be able to see the same kind of varnish on lots of rocks in the same area. This develops due to microbial activity on the rock. In desert areas, rocks often develop a shiny, black exterior called desert varnish. In the image to the right, the fusion crust is the thin, black coating on the outside of the meteorite. However, this crust weathers to a rusty brown color after several years of exposure on the Earth's surface and will eventually disappear altogether. It is often black and looks like an eggshell coating the rock. This thin crust is called a fusion crust. When a meteorite falls through the Earth's atmosphere a very thin layer on the outer surface melts. Meteorites which have fallen recently may have a black 'ash-like' crust on their surface. Since detailed analyses take time and money, look for the easy characteristics first. Sometimes, detailed chemical analyses need to be done, but only on rocks that meet all these characteristics. Usually, meteorites have all or most of these characteristics. You can use this list to guide you through them. Meteorites have several distinguishing characteristics that make them different from terrestrial (Earth) rocks. Several booms may be succeeded by irregular sputtering sounds, comparable to an automobile backfiring. Because the fireballs are traveling at high speeds, they sometimes produce a sonic boom or whistling heard 30 miles or more from where the meteorite lands. A smoke or dust trail is produced in the sky by the fireball caused by the removal of material from the surface of the meteorite. When a meteor enters the Earth's atmosphere the resulting fireball produces light, due to the friction between its surface and the air. Meteorites fall to Earth all the time and are distributed over the entire planet, so you could even find one in your own backyard! They are rocks that are similar in many ways to Earth rocks, but it is exciting to find a piece of another planet here on Earth. Meteorites are pieces of asteroids and other bodies like the moon and Mars that travel through space and fall to the earth. Do You Think You May Have Found a Meteorite?

Meteor vs meteorite