Don’t Throw Away that Hot Rock!

Attention metal detectorists and treasure/relic hunters! STOP!!!

Don’t throw away any hot rocks until you check and verify they are not meteorites. Meteorites are another kind of treasure you may encounter during your search.

Those of you who hunt gold nuggets and relics in the deserts of the southwest, Alaska, or anywhere for that matter have run across pesky hot rocks. These are highly mineralized rocks that make your metal detector sound off and make you think you found something good, even if only for a moment. Nugget-shooters, metal detectorists, and relic hunters have all kicked, thrown, or tossed hot rocks in the bushes at one time or another. It’s something that for most hunters is an everyday annoyance.

Meteorite hunters on the other hand, check the bushes, rock cairns and old dig holes (by the way; shame on anyone who doesn’t fill their dig holes!) for hot rocks that might be a meteorite; meteorites you may have inadvertently thrown aside and left for someone else to find.

Stone Meteorites may not look like anything special. But they will make your detector sound off and many a hunter has been fooled into thinking it was nothing more than a hot rock. Gold detectors are particularly useful in finding meteorites. Their extreme sensitivity that makes them good for gold nugget hunting, also makes them very sensitive to the iron content in meteorites. You simply don’t use discrimination. Stone meteorites contain a high percentage of nickel iron, higher than nearly any other Earth rock (one notable exception is Awaruite also known as Josephenite). These stony meteorites will set off the detector and will sound similar to a “Leavertite” hot rock. Iron meteorites are a bit more obvious and can easily be identified as an uncommon rock in the field.

It’s important to be able to identify a meteorite while in the field. There are a number of field ID methods and certain characteristics of meteorites you should be on the lookout for.

  • Magnetic: Because most meteorites have iron in them, this makes them magnetically susceptible. Keep in mind there are MANY earth rocks that will attract a magnet as well. Just because a rock is magnetically susceptible, does NOT mean it’s a meteorite. In fact, it is more likely to be Hematite or Magnetite. However, using a magnet is just the first step to identifying a rock as a potential meteorite. So, keep a rare earth magnet handy to test your hot rocks. Some meteorites will only slightly attract the magnet.
  • Heavy and/or Dense: Meteorites tend to be heavier than most Earth rocks both due to density and iron content.
  • Fusion Crust: Meteorites enter our atmosphere at thousands of miles per hour on a fiery course towards Earth’s surface. This causes the meteorite to have a burned look. It’s actually a glassy like thin melt crust on the outside of the stone, and will look like a charcoal briquette on freshly fallen meteorites. Older meteorites which have been weathering for hundreds or thousands of years could have residual fusion crust and a reddish or oxidized desert varnish exterior.
  • Regmaglypts: Meteorites, both iron and stone, can have regmaglypts, or “thumbprints”. These are depressions, scoops, and ridges on the exterior of the stone caused by ablation as the meteoroid enters our atmosphere. Material melts away from the meteorite and “burns off” leaving these thumbprinted like surface.
  • Streak Test: The streak test is used to rule out magnetite or hematite which will leave a streak on the non-glazed side of a bathroom tile. Most hunters I know don’t rely on this method, but have used it to identify some meteorwrongs. The logic is that meteorites don’t leave streaks, but this is sometimes unreliable because meteorites contain iron, and will oxidize. This oxidation will leave a “rusty” streak on the tile.
  • Windowing: Meteorite hunters will typically carry a piece of very course grit sand paper or a small pocket file in the event they find a meteorite. This aids in identifying possible meteorites when you sand or file a small “window” on an inconspicuous surface of the stone, exposing the interior. You’re looking for two things. Chondrules, and iron. 90% of stone meteorites are classified as chondrites. Chondrites are named for their chondrules (little spherules a few milimeters in diameter, with the matrix of the stone). Iron should also be visible as metal bits or flecks inside the stone too. Also, you needn’t worry about damaging the stone. Just find an inconspicuous place to file down to view the interior. It’s common practice to identify a stone as a meteorite. One word of caution, if the meteorite is heavily regmaglypted, do not file or break off a piece. Keep it whole and show it to someone with experience in handling meteorites.
  • Visual Examination & ID: Carry with you a 10X jeweler’s loupe. For most treasure hunters this is a common tool in their tool bag. Use the loupe to look for chondrules and the iron flecks within the stone. Use it to examine the exterior of the stone looking for signs of fusion crust. Also look for olivine crystals. Many meteorites may have visible greenish colored olivine crystals within the matrix of the stone.

If you have found a rock that meets all of the above criteria. you MIGHT have a meteorite! It’s still a good idea to have your rock identified by an experienced collector, hunter, or scientist familiar with meteorites. Do NOT take it to a geologist. Most geologists are not trained in meteorites. Let’s put that statement in perspective. Would you take your car to a brake specialist to fix the transmission? Just because someone works with and studies rocks, does not mean they know anything about meteorites.

Meteorites are rare, some more rare in fact than gold or diamonds. But they are found in every state of the USA, and on every continent on our planet. As of this writing some 50,000 plus meteorites have been found, classified and cataloged throughout the world.

If you have a question or think your “hot rock” might be a meteorite. Feel free to email us in focus and sunlit pictures for evaluation.

This post is based, in part, on content licensed from E. Wichman from the defunct website that was purchased by SkyFall Meteorites. 

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