How Do you know if it is a meteorite?
The purpose of this page in not to make you an expert at identifying meteorites. It is to help save time and money by eliminating things that are not meteorites. Probably 99% of the items that are presented by finders as meteorites turn out to be not to be meteorites. There are a number of features that can be used to help identify if you have a meteorite or not. Rather than start with meteorite features, since most rocks are not meteorites, lets start with things that will help eliminate rock as being possible meteorites.
Keep in mind that none of these features is 100% conclusive. So far no rock from earth has ever been identified as having been blasted into space and returned as a meteorite. But, that doesn't mean it couldn't happen. If any of the terrestrial features below are found with some of the meteorite features listed below it should be looked into further.
Terrestrial (earth) Features that indicate a rock is not a meteorite.
1. If there is quartz (a clear or milky white crystal) it is not a meteorite. As far as I know quartz has never been found in any meteorite.
2. If there is an easily visible crystal structure it might not be a meteorite. This is not conclusive because some of the rarer meteorites do have some crystal structure. However, most ordinary meteorites do not unless viewed under a microscope.
3. If the rock has many small holes in its interior it is probably not a meteorite. Small holes are almost never found in the interior of meteorites. The one or two that do have them are extremely rare.
4. If the rock feels light it is not a meteorite. Stony meteorites generally have a density around 3.5 grams per cm3 and normal earth crustal rock is around 2.7 grams per cm3. In other words stony meteorites are about 30% heavier for the same size rock. The opposite is not true however. A rock that is denser than normal does not have to be a meteorite. There are many examples of dense terrestrial rocks.
5. If the exterior has sharp pointed features (except on obviously broken surfaces) it is not a meteorite. As meteorites come through the atmosphere any sharp points are melted away. As a result meteorites have smooth surfaces, although they may have depressions, called regmaglypts, that look like thumbprints pushed into clay.
Pictures of some common meteor-wrongs
A brief description is below each picture. Each picture has been thumbnailed to make the page load faster. If you click on the pictures you will see the full image. The pictures with DF at the end were graciously provided by Dave Freeman.
ball. These are used in ore crushing operations to reduce the ore
to smaller sizes. They are generally round in shape and can come
in various sizes from 2 inches up to at least 6 inches in diameter.
|Rusted magnetite. Magnetite is one of the most common meteorwrongs. Notice the rough surface texture. DF|
| Eroded and
wind polished cretaceous hematite. The piece on the left looks
nice and smooth like you might expect from a meteorite. The piece
on the right has small surface pits. DF
|Iron ore from Atlantic City, Wyoming DF|
|Coal fired locomotive clinker. Notice the numerous small holes. DF|| Lucite Hills
oil shale with iron pyrite encrusted oolites. This is a slice that
shows circular inclusions that look like chondrules. DF
|Smelter ore, titanium 16%. Note that the surface is rough and not smooth. DF||Worm coprolite hematite
encrusted. The surface has some linear
"cliffs". These are from a layer of the rock chipping
away. Meteorites don't have layers and as a result don't have
these type features. DF
|This is not a meteorite. It is a rock with desert varnish. Notice how bumpy the rock is instead of being smooth like the others.|
Now that we have thrown away 90% of our rocks lets look at some meteorite features that will help identify a meteorite.
Features that indicate a rock is a meteorite.
1. Fusion crust is what forms as a meteor passes through the atmosphere. It is the melted exterior of the meteor. Because meteorites are composed of different materials not all fusion crusts look the same. Fresh fusion crusts are usually a matte (dull) black, but some fresh meteorites have crusts that look like shiny black plastic and others are a light yellow brown color. Once a meteorite is on the ground it starts weathering. This weathering causes an oxidation of the crust and it turns from black to brown in color. Depending upon the climate conditions where it falls this will take varying amounts of time.
Fusion crust is one of the more difficult things for a novice to get a good feeling for. It really requires looking at a number of different meteorites. Many people picture the crust as being like the skin on an orange, but it is much more like the skin on an apple. Fusion crust is very thin, usually less than 1mm thick. It is generally the thickness of a heavy piece of paper. Out west it is many times confused with desert varnish which is a dark coating on rocks exposed to the sun and elements for a long time. Below are pictures that show both.
2. Most meteorites contain large amounts of iron and as a result are attracted to a magnet. This is not definitive because some meteorites are not attracted to a magnet and many earth rocks are. However, it is another clue for separating the trash from the treasures.
3. If the interior of the meteorite is visible, there are a couple clues. If it is an ordinary chondrite it will have small flecks of metal. The flecks may not be visible on a broken weathered surface, but if you grind a fresh surface they will be visible except for extremely weathered chondrites. Native terrestrial iron is extremely rare and found in only three locations. If you find metal flecks it is a very good indication of a meteorite.
4. Chondrules may also be visible on broke surfaces. Sometimes they are whole and look like little round balls sticking out of the surface.
Fusion Crust Pictures.
A brief description is below each picture. Each picture has been thumbnailed to make the page load faster. If you click on the pictures you will see the full image.
|This picture shows a 100% crusted Nuevo Mercurio (H5) meteorite. This black crust is what an ordinary chondrite looks like just after a fall.||This picture shows a 100%
crusted Gao-Guenie (H5) meteorite. These pieces fell in 1969 and
were recovered only recently. Notice the crust has weathered to a
|This picture is of a 1/2 Jengcheng (H5) stone. Notice how thin the crust is. This is a typical thickness.||This is picture of a slice of
Sahara 97094. Notice the 2 parallel black lines which show the
thickness of the crust. These lines are about 1mm apart.
|Different types of meteorites
can have different crusts. This is a carbonaceous chondrite,
|This piece is from an aubrite called Cumberland Falls. Notice the very thin almost yellowish crust.|
|This is a howardite, Great Sand
Seas 010. The crust is a shiny, black that is almost plastic looking.
It also has flow lines where melted crust flowed in streams pushed by
the atmosphere during entry.
The next pictures are not fusion crust pictures, but show what the interior of a couple ordinary chondrites look like.
|This is a super slice of Sahara 98175 an LL3.5 Notice the abundant chondrules as well as several large light colored clasts.||This is a piece of the El
Hammami meteorite. Notice the numerous metal flecks. If you
look closely you can also see some small gray chondrules.
Now that you know all about meteorite ID here are a few more pictures for you to look at and try to identify.