Some meteorites, such as stony meteorites, contain only a small amount of metal, but will attract a magnet hanging on a string. Metal detectors can alert you to whether a rock contains metal, but not all metal is magnetic. For instance, aluminum sets off metal detectors but is not magnetic. So, if you find a rock with a metal detector, try the magnet test too.
In addition to meteorites containing iron, there are man-made and naturally-occurring materials that are magnetic and are easily confused with meteorites.
Magnetite and hematite are common iron-bearing minerals that are often mistaken for meteorites. Both minerals can occur as large masses with smooth surfaces that are heavier than typical rocks, but have some features which resemble meteorites. Magnetite is very magnetic hence its name and hematite is mildly magnetic. Use the streak test below to distinguish these minerals.
The most common meteorites to fall on Earth are called chondrites. You need to break open the meteorite to see the chondrules. It isn't always easy to identify a meteorite even using the properties discussed above, because some characteristics are shared by common terrestrial rocks and man-made materials.
Let's look at some areas where confusion can arise. Meteorites are almost never perfectly round or spherical and rarely are they aerodynamically shaped. They are usually very irregular in appearance and come in a variety of different shapes and sizes. Many people believe that meteorites have the appearance of being molten, perhaps having a frothy appearance or bubbles on their surfaces.
However, this is not the case. The outer portion of a meteorite, the fusion crust, is either smooth or has the characteristic regmaglypts thumb prints described earlier.
However, many terrestrial igneous rocks are porous and have holes in them. These holes or 'vesicles' were produced by bubbles of gas that formed in the magma as it was erupted.
If you find a rock that is porous or contains vesicles it is a terrestrial rock. If there is quartz a clear or milky white crystal it is not a meteorite. Quartz is produced on the earth in evolved rocks at plate margins; in contrast, other planetary bodies like asteroids do not have these kind of settings and do not produce large quartz crystals.
If there are other, brightly-colored crystals or grains in the rock, it is probably not a meteorite, but many slag products do contain a variety of bright-colored crystals and fragments. 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. Irons may be covered with a flaky layer of iron shale on the surface. This is not a meteorite. This is a piece of man-made iron.
By testing for nickel-iron, you can determine if the object is a true meteorite or a meteor-wrong. This is a stone Gao Meteorite. Note the block shape with smooth rounded corners. The fusion crust is mostly still black, but some spots of brown are appearing with age. Contraction cracks can be seen in the fusion crust.
It is domed and more round than some because it is an oriented meteorite that fell through the atmosphere in stable flight causing melting on only one side. This is an Agoudal Meteorite. Note the thumb printed surface, unusual shape, and weathered appearance. Will be strongly attracted by magnet because it contains iron. Meteorites are Solid, not Porous The slag from industrial processes of manufacturing iron and steel can have metallic particles in it.
Which Are Meteorites? No, this is black lava. This is a porous lava rock which is very common to find in the desert. Black lava is black throughout. Meteorites are not normally completely black. Very small and lightweight pieces of lava rocks may stick weakly to a magnet, but whole rocks will not hold a magnet. No, this is Limestone Rock. Black limestone with a naturally etched surface texture. Will not react to a magnet at all. Similar textured rocks are commonly seen on dry lake beds.
Meteorite Color When meteorites are fresh, they are often black, and their fusion crusts may show flow lines and details that can help in identification. This is a real meteorite named Nuevo Mercurio. It is an H5 chondrite and will be strongly attracted to a magnet.
It was a witnessed fall, and many specimens are fresh with black fusion crust. This is a genuine meteorite, and the red color is from rusting metal coming through the fusion crust. It has an irregular shape and rounded off corners.
It is slightly weathered from years on Earth but has not begun to crack apart. This Is Not a Meteorite. This stone is Brown Basalt. Basalts are igneous rocks that are found in many colors and are everywhere in the desert. They are usually porous though this one is not very porous. They can occasionally be slightly responsive to a magnet. No, this is not a meteorite. It is a red and black slate type rock, there is no response to a magnet.
Sometimes the red of rocks resembles the rust spots on real space rocks. Meteorites are Heavy and Have Metallic Iron Meteorites are generally heavier than earth rocks of the same size. Magnet Test The vast majority of meteorites contain some metallic iron while others are mostly solid iron.
Both Magnets Stick. Which One Is The Meteorite? This is Hematite. Some pieces of Hematite are not responsive to a magnet, and some are. Hematite nodules can resemble actual meteorites and are among the most commonly misidentified stones. This is a real meteorite. Many stone types and of course all iron meteorites will respond to a magnet. Even low metal chondrites will stick to a rare earth magnet. Some achondrites contain so little iron however that they will not respond to a magnet.
Streak Test It is a common practice in geology to rub a mineral or rock across a streak test plate and observe the color of the mineral powder line that is made.
This is a Hematite streak and not a meteorite streak. Since the dawn of man's history, the red powder of hematite has been used as a pigment by humans. Although the rock may be dark brown or grey on the exterior, the powder when ground up will be red. The picture shows a diamond file has been used to test a piece of rock. Yes, this is a real meteorite streak. Many stone meteorites will usually produce a brown color when ground off with a diamond file or tested on a streak plate.
Metal Grains The largest group of space rocks is the chondrite type of stone meteorite, and they contain nickel-iron metal in the form of tiny grains scattered throughout the matrix of the rock.
Which Stone Contains Metal Grains? This is common. Also, note that many of these stones exhibit visible metal flakes when cut. A more oxidized meteorite might not have any of these left, but a polished stony meteorite will almost always still have some of these. Flecks of specular hematite in terrestrial rocks can look similar, but appear darker, and less like native metal.
Also — shock veins. When asteroids collide with each other in space, they can do so at thousands of miles per hour. Some become truly broken up and brecciated, while others get only a few thin, usually black, veins of melt. Here are some examples:. Not all meteorites have these, but they can be a good indicator. Stony meteorites without chondrules are very rare, and they usually look very much like terrestrial igneous rocks on the inside. The only good identifying features of these types of meteorites are shock veins and fusion crust.
These meteorites rarely oxidize over time. In 15 years of hunting in good desert terrain, we have found three such meteorites. Here are some examples. Iron and stony-iron meteorites are very rare, but are easy to recognize. All of the above meteorites would be very strongly attracted to a magnet. As much as a piece of solid iron. But be careful — many terrestrial rocks also contain magnetic iron, and people have been concentrating iron to make tools and thus, slag , for thousands of years.
Most iron-bearing, magnetic rocks on Earth are from Earth. Which raises an important idea: if hunting for meteorites, it is very important that you be familiar with characteristics that meteorites do not have.
Many meteorites have been found by people familiar with rocks, their surroundings, their farms, etc. Below the large crack on the left the fusion crust is thin and what appear to be clasts are visible. I would like to see the inside of this one. We cannot see the whole stone but what we see looks flatter than most. Fusion crust with contraction cracks. Photo credit: Dawood Ghasemi. The fusion crust is largely intact.
There are a few regmaglypts. Shiny fusion crust, crust has contraction cracks, and some crust has chipped off. Shiny fusion crust but some has chipped off. There are no contraction cracks in the crust.
Minor regmaglypts. Rounded shape. Shiny fusion crust, but a much rougher surface than is typical. Shiny fusion crust. This appears to be another oriented stone with flow lines. Shiny fusion crust with few contraction cracks.
Many regmaglypts. Shiny fusion crust covers rounded, unbroken surface. Some fusion crust has chipped off. Rusty metal grains on the broken surface. Rounded shape with nearly complete fusion crust that is not shiny in this light. The crust has contraction cracks. Interior is lighter than the fusion crust. Unusually spherical stone with a cracked fusion crust. These photos were all sent to me in
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