If you've come across a rock that doesn't appear to belong to this world, there's a chance it's a meteorite. Although meteorites are relatively rare on Earth, it is not impossible to find them in nature. However you have to make sure that the rock actually comes from space and is not an ordinary earth stone. By verifying the presence of the typical hallmarks of a meteorite it is possible to determine if the rock you found is indeed of extraterrestrial origin.
Steps
Part 1 of 2: Examine the Appearance of the Rock
Step 1. Check if the rock is black or rust colored
If it is a freshly fallen meteorite, it will be black and shiny to be burned through the atmosphere. After a long time on Earth, however, the meteorite's metal turns to rust, causing it to turn a rusty brown.
- This rust begins with small red and orange spots that slowly expand to cover the surface of the meteorite. You should still be able to see the black crust even if it has started to rust.
- The meteorite can also be black in color with slight variations (for example with leaden or bluish shades). However, if the color of the rock you found doesn't come close to black or brown at all, then it's not a meteorite.
Step 2. Check if the rock has an irregular shape
Contrary to what one might expect, most meteorites are not round; they are generally quite irregular, of various sizes and shapes. While some may develop a conical shape, they typically don't have an aerodynamic appearance once landed.
- Although irregular in shape, most meteorites have rounded, blunt edges.
- If the rock you found is relatively normal in shape, or is round like a ball, it may still be a meteorite. However, the vast majority of meteorites have an irregular conformation.
Step 3. Determine if the rock has a melt crust
As meteoroids pass through Earth's atmosphere, their surface begins to melt and the pressure of the air pushes the molten material back. The result is a smooth surface, which appears to have partially melted, called a “melting crust”. If your rock exhibits these characteristics, it could be a meteorite.
- The fusion crust is generally smooth and uniform, but it can also have marks, drops or ripples where the stone has melted and solidified again.
- If the rock doesn't have a melting crust, it most likely isn't a meteorite.
- The melt crust may look like a black eggshell covering the rock.
- Rocks found in the desert sometimes develop an outer layer that appears very similar to a melt crust. If you have found the rock in a desert environment, be aware that the black of its surface may simply be due to the desert patina.
Step 4. Check for flow lines
These are small streaks on the melting crust that were created when the surface was melted and pushed back towards the back of the meteoroid. If the rock has a crust-like surface crisscrossed with small streaks, there's a good chance it's a meteorite.
Flow lines may be very small or not immediately recognizable with the naked eye, as they may be interrupted or not perfectly straight. Use a magnifying glass and pay close attention when examining the surface of the rock
Step 5. Note any craters and depressions
Although the surface of a meteorite is generally smooth, it can also have more or less deep cavities that resemble fingerprints. Look for them on the rock to determine if it is a meteorite and what type of meteorite it is.
- Ferrous meteorites tend to merge very irregularly and will have deeper and more defined cavities, while stony ones may have smooth craters like the rest of the surface.
- These indentations are known in technical jargon as "regmaglipti", although for most people who work with meteorites in English-speaking contexts it is sufficient to call them "thumbprints".
Step 6. Make sure the rock is not porous or full of holes
Although the craters and cavities on the surface may indicate that the rock is a meteorite, no meteorite has holes in it. Meteorites are composed of compact and solid material; if the rock you found is porous or has bubbles, unfortunately it is not a meteorite.
- The rock is definitely not a meteorite if it has holes on the surface or appears full of bubbles.
- Waste from industrial processes is often confused with meteorites, even if they have a porous surface. Other types of rock that are commonly misleading are lava rocks and black limestone ones.
- If you have a hard time distinguishing between holes and clips, it may be helpful to go and look online at the visual comparisons of these features to learn how to tell the difference.
Part 2 of 2: Testing the Physical Properties of the Rock
Step 1. Calculate the density of the rock if it seems heavier than normal
Meteorites contain metal, so they are very dense. If the appearance of the rock you found makes you think it may be a meteorite, compare it to other stones to see if it is relatively heavier than normal, then calculate its density to determine if it is actually a meteorite.
You can calculate the density of the potential meteorite by dividing its weight by its volume. If the result is greater than 3, it is much more likely that it is a meteorite
Step 2. Use a magnet to check if the rock is magnetic
Almost all meteorites have magnetic properties, even minimal ones, due to the high concentration of iron and nickel. If the magnet isn't attracted to your rock, it's almost certainly not a meteorite.
- Since many terrestrial rocks are also magnetic, this test will not conclusively prove that the rock in question is a meteorite. However, failure to pass the test indicates that it can most likely be ruled out.
- Ferrous meteorites are much more magnetic than stony ones, and many are powerful enough to interfere with a compass placed near them.
Step 3. Rub the rock against the unglazed ceramic to see if it leaves a streak
The smear test is a good way to rule out that you have common earth material in your hand. Scrape the rock against the unglazed side of a ceramic tile; if it leaves any trace other than a faint gray streak, it is not a meteorite.
- You can use the unfinished side of a bathroom or kitchen tile, the unglazed bottom of a ceramic bowl, or the inside of a toilet cistern lid.
- Hematites and magnetites are commonly mistaken for meteorites. Hematites leave a red streak, while magnetites leave a dark gray one, revealing that they are not meteorites.
- Keep in mind that many terrestrial rocks also leave no streaks; Although the smear test can rule out hematites and magnetites, it will not be sufficient to prove with certainty that your rock is a meteorite.
Step 4. File the surface of the rock and look for shiny metal flakes
Most meteorites contain metal; it is possible to see the reflections under the melting crust. Use a diamond file to scrape off a small portion of the surface and check inside for metal.
- You will need a diamond file to scratch the surface of a meteorite. It is a process that takes time and a lot of effort. If you can't do it yourself, you can go to a specialist laboratory.
- If the interior of the rock is homogeneous, it is most likely not a meteorite.
Step 5. Inspect the inside of the rock to see if there are any small balls of rock material
Most meteorites that fall to Earth have small round masses inside known as "chondrules". They can resemble smaller rocks and vary in size, shape and color.
- Although chondrules are generally located inside meteorites, erosion caused by long exposure to the elements can cause them to appear on the surface.
- In most cases it is necessary to break the meteorite to check for the presence of chondrules.
Advice
- Since meteorites tend to have higher nickel concentrations than terrestrial rocks, a test for nickel can be used to determine whether the rock is a meteorite or not. This test can be done in any meteorite analysis laboratory and is more indicative than most other tests.
- Meteorites can have bubbles, called vesicles. All lunar meteorites are vesicular; stony or ferrous meteorites do not have bubbles inside, but some of the stony ones may have bubbles on the surface.
- There are tons of books and websites dealing with this topic. Do some research!
- The chances of finding a real meteorite are very low. Deserts are the best places to look.
