Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay
People tend to mistake many terrestrial rocks for meteorites. Commonly mistaken objects include:
|Slag and waste metal are especially often mistaken for meteorites. Meteorites do not melt except for a thin surface layer. They do not flatten against the surface they hit, or enclose objects they hit. If it's obviously flattened against a surface or encloses terrestrial objects, it is not a meteorite.|
| Slag is the fused silicate residue from smelting ores. Often similar in composition to natural igneous rocks and can be hard to tell from them. Ropy textures on the surface are common, as are shiny or iridescent tarnishes. |
| Clinker is the fused silicate residue from burning coal. Has lots of bubbles or vesicles, often inclusions of brick fragments, pebbles, and other debris. Colored tarnish or films on surfaces are common. The cavities and embedded objects rule it out as a meteorite. |
|Metallic meteorites are always nickel-iron alloys and always magnetic. Any non-magnetic metal is not a meteorite. If the magnet does not stick to the underside of the object without aid, the material is not magnetic. These are examples of non-meteorites.|
The embedded objects rule this metal out as a meteorite.
|Meteorites develop a thin fusion crust while entering the atmosphere, but people often mistake any shiny surface for melting. Volcanic rocks, of course, really were molten. Other shiny surfaces can be due to weathering or mechanical action.|
Most rocks fall in the density range of 2.5 to 3 times as dense as water, and rocks at the upper end of the range are noticeably denser than those at the lighter end, even just hefting them by hand. Some dark igneous rocks can have densities of over 3 times as dense as water, and iron formations can be five times denser than water. Real meteorites are dense, but density alone doesn't make a meteorite.
Many dark colored igneous rocks have densities above 3 grams per cubic centimeter and are noticeably heavy. Ore minerals often have densities above 5 grams per cubic centimeter.
Many artificial materials are magnetic, but so are magnetite and a number of other minerals. A lot of magnetism is wishful thinking. I've seen people claim that completely non-magnetic materials "seem" to attract a magnet. If the magnet doesn't stick to the material when you turn it upside down, it's not magnetic.
|Real meteorites do not contain internal cavities. The famous meteorite on display at the American Museum of Natural History in New York does have deep surface pits from weathering, but that's how most cavities in rocks form. Cavities alone do not make a meteorite.|
|This is dolomite with solution cavities, not a meteorite.|
|Crystal-lined cavities like in this rock do not occur in meteorites. This rock is dolomite. The crystals are quartz stained by iron oxide. The light color of these two samples rule them out as meteorites.|
|The dark igneous rock gabbro is often mistaken for meteorites. The sample shown here is developing spheroidal weathering. Gabbro's tendency to weather into odd shapes and develop surface stains on weathered surfaces often make it look unusual.|
|Odd shaped rocks of all sorts are mistaken either for meteorites or artifacts. This one is neither. It is merely a rock with a resistant vein in it that weathered a bit more slowly than its surroundings.|
Return to Mineralogy-Petrology Index
Return to Thin-Section Index
Return to Crystals and Light Index
Return to Crystal Structures Index
Return to Mineral Identification Tables
Return to Professor Dutch's Home Page
Created 22 April, 2005, Last Update