Colorado is host to 80 known meteorites, the fourth largest number in any state following Texas, Kansas, and New Mexico. A majority of these meteorites were found many years after they fell, usually by farmers after plowing their fields, and are known as “finds”. However, in rare cases newly fallen meteorites are correlated visually with a fireball and thus are called “falls”.

The best resource for Colorado meteorites is – you guessed it – the Handbook of Colorado Meteorites by our own Matthew L. Morgan, the Deputy Director and Senior Research Geologist at the CGS.

Artist's rendition of a fireball over Maroon Bells
Artist’s rendition of a fireball over Maroon Bells.

Meteorites are divided into three basic categories: iron, stone, and stony-iron. These divisions are based on the percentage of total nickel-iron in the meteorites: the irons contain about 98%, the stony-irons about 50%, and the stones less that 23%. Nickel-iron in any amount usually indicates that a rock is a meteorites, because it is rarely found in terrestrial rocks.

Johnstown meteorite, a stony meteorite
Johnstown meteorite, a fall from Johnstown, Colorado. It is a type of stony meteorite called a diogenite.

Recognizing a meteorite can be done in a few simple steps. The first is to test whether or not the meteorite is magnetic. This can be done by determining whether the meteorite will attract a kitchen magnet. The surface of a meteorite may display regmaglypts, or “thumb-prints”. These are not holes such as those common to igneous rocks, but are shallow indentations similar to those created by pushing your thumb into potter’s clay 5-15 mm deep. Immediately following the fall of a meteorite, the surface will look black with fusion crust. If the meteorite goes undiscovered even for a few months, especially in warm, damp climates, this black surface can oxidize and turn brownish-red.

Map of Colorado meteorite locations