Exterior characteristics

     Immediately preceding the fall of a meteorite the exterior looks black, similar to that of charcoal. This burnt surface of the meteorite is called fusion crust (see image at right).  It may cover the surface of a fresh meteorite like tar and give its edges a rounded appearance.  Meteorites are rarely ROUND!

Weathered fusion crust.  The two stony meteorites shown above were collected many years after they fell.

In the later stages of weathering, a rind of oxidized material can form around the meteorite that looks similar to rust (see image at right).  This iron oxide (rust) coating, virtually replaces the original fusion crust.

     The size of a meteorite varies greatly, but most people recover meteorites that are the size of a baseball or larger, up to a few feet in diameter.  Meteorites, overall, are heavier than most earth rocks. Stony meteorites are about 1.5 times more heavy than a similar sized earth rock, while iron meteorites can be 3 times as heavy!

Interior characteristics

     Weathering is also taking place on the inside of the meteorite as well. When sliced, most fresh stony meteorites exhibit small flakes of shiny metal and a gray matrix. Over time, this metal may oxidize and disappear into the matrix material which turns tan to brown when oxidized. Chondrules, characteristic of most stony meteorites, usually remain intact throughout the weathering process. However, they too can fade into the background material of the meteorite and may exhibit beautiful coloration. 

Chondrules are spherical masses of mineral material found on cut surfaces of most chondritic meteorites.

Widmanstätten pattern on a cut and etched slice of the Bear Creek, Colorado iron meteorite.

Quick tests

     The easiest test one can perform on a suspected meteorite is to grind off a corner of the suspect and look for small flakes of metal.  Iron meteorites will look like chrome.

Tie a magnet to a string and see if it is attracted to the rock. Does it swing toward it?

Once a corner is ground off and it passes all of the above tests, DO NOT harm it in any other way. Leave it alone and give us a call.  We will gladly inspect the specimen up-close and maybe even make you a cash offer for it.

Fusion crust. An outstanding example of fresh fusion crust on this recently collected stony meteorite.

     Fusion crust is a thin skin of melted material, usually only 0.5 mm thick, that results when the meteor passes through the earth’s atmosphere. If the meteorite goes undiscovered, even for a very short period of time and depending on climate, this fresh black surface can oxidize and turn a brownish-red color (see images at left).

     The surface of the meteorite may also be covered in regmaglypts or "thumb-prints" (see top image below). These indentations are most common on iron meteorites, however they do occur on stone meteorites as well. Regmaglypts form when minerals within the meteoroid melt at different temperatures while passing through the earth’s atmosphere and normally range from 5mm-15mm deep and 10mm-30mm wide. 

Thumb-prints are shallow indentations (not holes) caused by differential melting of components in the meteorite.

Weathering rind on an old meteorite.  The rusty appearance of a weathering rind indicates that the meteorite has been exposed to the elements for an extended period of time. Notice that the original fusion crust has virtually disappeared.

Shiny metal on a cut and polished surface of a fresh meteorite.

     The inside of iron meteorites look completely metallic. If a piece of an iron meteorite is sliced off and brushed with a dilute solution of nitric acid (DO NOT attempt this without proper training!!), a Widmanstätten pattern appears (see image at left). This cross-hatch pattern forms from the minerals kamacite and taenite and is very beautiful when properly etched.

     Due to the abundance of metal in most meteorites, they will attract a magnet, with a few exceptions. This can be a great test to use in the field as even a kitchen magnet will be attracted to a meteorite.

Meteorite checklist

• Color - Brown to black; fusion crust

• Weight - Generally heavy for its size.

• Will normally attract a magnet.

• Thumb prints - small indentations, not bubbles or holes.

• Metal or chrome surface when ground on-edge

• Most stone meteorites will contain chondrules.