So, you have found an unusual rock, and you wonder if it is a meteorite? Neat!

Preserve scientific value

First, if it really is a meteorite, then we need to preserve as much of the scientific value as we can, so when it is studied we can learn much more about it. That means we need to avoid contaminating the rock from this point onwards. That means:

• Don’t stick magnets to it!
• Don’t dunk it in water!
• Don’t handle it with bare hands!

(Oops, you’ve done some of that already? OK, let us minimise any further contamination from this point forwards. Make a note of anything you have already done, so that can be reported later).

Photograph In Situ

Hopefully, you haven’t collected the rock yet. We want to take photographs of the rock in situ. Take images from above and from various points around the rock, looking in different directions. Take them close up, and take them from further back so the context can be seen. If you do not have geotagging of your images turned on in your smart phone, record the exact location of the find. If you do not know how to get the exact position of this location using your phone, turn on location services in your privacy and security settings, and allow your camera to use location services, then take the images. This will add meta-tags to the images of the location they were taken that researchers will later be able to use.

Collect Carefully

To collect the rock, place a piece of aluminium kitchen foil over the rock, then pick it up using the foil as a protective sheet between you and the rock.

Wrap the rock in the foil and place in a ziplok plastic bag. Place the sealed bag with the rock in it inside a refrigerator any time it is not being studied or transported.

Initial Study

OK, once we are ready to study the rock more closely, and we have protected it from contamination, we can make some initial observations that do not require specialist equipment. Put on some examination gloves, and unwrap the rock.

Reference Images

Now, let us obtain some good reference photographs. Before you send the rock to researchers, they will be wanting to see some good photographs of the object. You want to place the rock in light that is not harsh direct sunlight, but is well illuminated from all sides. Outside on a cloudy day is ideal. Turn off any and all “filters” or other image enhancement options. You want to take as unprocessed a photo as it is possible to take on your smart phone.

Place the rock on a plain white sheet of paper. Next to the rock, place a ruler with millimetre graduation markings. Take photos from directly above the rock. Don’t get too close, as that results in image distortions. Make sure the ruler is in focus. Rotate the rock so you can take photos of different sides of the rock from the same perspective, above.

Close Examination and Images of Details

Now look closely at the rock. Are there already any chips or damage to the surface of the rock? Things that reveal detail about the rock without imposing any damage to the rock? If you can see chips or similar, take a close-up photo of these sorts of areas – holding the ruler up close to the chipped surface as you do so.

What we are looking to see is what the inside of the rock looks like, and especially if the chip reveals any thin dark outer crust. That could have formed when a meteorite fell fast through the atmosphere, heating up as it fell. However, this is not determinative, as you can get a ‘skin’ on volcanic rocks or rocks that have weathered and been subjected to chemical reactions that created a ‘rind’ on the rock.

We’re also looking to see if the chip reveals any crystal forms. One thing that is indicative of a rock probably being terrestrial in nature is if it has light-coloured crystals – if these turn out to be quartz, that indicates that it is not a meteorite. But the presence of pale components does not mean it is not a meteorite, if for instance these are things like calcium-aluminium inclusions instead of quartz crystals. There is not one single determinant colour for meteorites; some can have consistent internal structures, and others can be jumbled aggregations of various globules.

We also want to take close-up images of any pits or dimples in the surface of the rock. Iron-nickel meteors in particular tend to have dimples or hollows on the surface, called regmaglypts – some rocky chondrite meteorites may also have regmaglypts.

Are there any ripples in the surface of the rock, especially ones radiating out from a point in the middle? Those could be flow lines from the melting fusion crust rippling as the rock fell through the atmosphere. Hold the ruler close and take close-up images.

Are there any globular protrusions on the surface? Image those carefully too, as they might indicate the presence of chondrules.

Well-rounded rocks are often not meteorites. That shape comes from alluvial wearing over a long period of time.

Things that could indicate a rock is not a meteorite:

• “Bubbles” (vesicles) are often an indication that a rock is volcanic in origin, or possibly man-made (slag from smelting is surprisingly common to find in places that you might not expect it).
• Fossilised remnants e.g. shells

Mass, Volume, and Density

Now to collect more data about the rock. Using an accurate set of kitchen scales that can measure in grams, zero the scales and place the rock on the scales. Record the exact weight in grams.

We really want to know the density of the rock – and to figure that out we need not only the mass (that we just measured) but also the rock’s volume. Now if the rock has definitely already been wet by the weather and environment, we could use a water bath to measure the volume. If it is believed to be a freshly-fallen meteorite, however, we don’t want to go dropping it in water just yet. Instead, you may be able to use a smart phone with a lidar scanner to estimate the volume of the rock. If the rock has already been contaminated with water, you can use this method to determine the volume of the rock:

• Place a tray on an accurate set of scales and zero the scales.
• Place a container big enough to completely contain the rock on the tray
• Fill the container with water to the very top
• Carefully place the rock into the container without splashing. This is the hardest part. You just want the water to overflow the container into the tray only.
• Are there air bubbles around the rock, perhaps due to regmaglypts? You might need to reach in and rotate the rock to release the air bubbles.
• If dropping the rock and maybe reaching in and rotating it resulted in the water level in the container now being below the level you originally filled it to, use a pipette to suck water up from the tray and add it to the container until the water level is back up to the top again.
• Carefully remove the container from the tray, being careful not to spill water into the tray, and letting water on the outside of the container drip off into the tray.
• Record the measurement on the scales. This will be the weight in grams of the water displaced from the container. We can use that mass of water to determine volume, as 1mL of water = 1g. The volume of the water displaced by the rock is exactly the same as the volume of the rock.

If you think this is a freshly fallen meteorite, and you don’t know how to use a lidar scanner to calculate volume, or you don’t have one of those on your phone – don’t worry about it. Leave the density calculation to the experts.

Once we know the mass and the volume of the rock, we can calculate the density of the rock, using mass / volume. This number in itself is not determinative, but many meteorites are more dense than terrestrial rocks. Iron-nickel meteorites could be as dense as 8g/cm³, but rocky condrites could be 2 to 3.5g/cm³ – similar to many terrestrial rocks.

Streak Test

You can also do a streak test: You need some unglazed ceramic material. Most people do not have this lying around. What you really need to do is purchase an “unglazed mineral streak plate” intended for geologists. You can purchase these online from suppliers catering to geologists, and even on Amazon. Find a spot on the rock you want to test, a bit that sticks out, and rub the rock firmly on the streak plate. Observe the streak plate: if you see a black or red streak, it is unlikely to be a meteorite. If you don’t see a streak, it could be a meteorite.

Magnetism

It is possible to do a test for response to a magnet, but you really shouldn’t. It isn’t conclusive for a start. There are terrestrial minerals that are magnetic, and some that are not. Some meteorites will be magnetic, but some will not be.

Whatever you do, don’t stick a magnet to the side of the rock. This could modify the internal magnetic direction of crystals in the meteorite, reducing the scientific value of the find.

If you absolutely must attempt to test for magnetism – though again, anything you find will be inconclusive! – tie some string around the rock in such a way that it will not fall out, then suspend the rock in the air. Allow time for the rock to stop swinging or twisting. Prop your smart phone up to video the next bit, zoomed in on the rock. Bring a magnet close to the rock, and see if the rock moves toward the magnet or twists. Then stop doing it and put the magnet away. You can review the video to check to see if the rock moved at all. You don’t need to keep repeating the test or tapping the rock with the magnet. But honestly… leave the tests for magnetism to the expert researchers.

Contact Experts

Speaking of which, at this point you will have made a bunch of observations and collected data that may not be conclusive, but may not have eliminated the possibility of your find being a meteorite. The next step is to get a geologist to consider the evidence. Sent an email to meteorites@rasnz.org.nz with your images, your data and other information you have been able to collect about the rock.

If the researchers think that the find could be a meteorite, they will probably want to examine the rock themselves. They will make arrangements with you for the transfer of the rock to them, and work out with you what happens to the rock after they have studied it.

Please do note that researchers will probably want to physically modify the rock (damage it). They will be looking to expose the rock’s crystalline structure, looking for inclusions and nodules as they microscopically examine it. This may be a small chip, or they may want to ‘section’ the rock, cutting it completely open. They may acid-etch looking for various structures and crystals.