The surface is too rough for a meteorite

For small meteoroids, 90% of the mass is lost to ablation as they come through Earth’s atmosphere. Edges, corners, rough surfaces, and any protuberances are the first parts to ablate away. Put an ice cube in water and wait for 90% to melt. The “cube” that remains will have no edges or points. It is like that with meteorites. As a consequence, most stony meteorites have rounded and smooth exteriors, except where they have broken.

Two views of meteorite Northwest Africa 7496 (polymict eucrite). This is a typical meteorite in being rounded and having a dark, glassy fusion crust, except where the meteorite has broken. Photo credit: Randy Korotev

Meteorites do break apart in the atmosphere and that can lead to some rough surfaces. See the Ash Creek samples below.

Meteorwrongs from temperate climates

All the photos below were sent to me by persons who wanted to know if the rock was a meteorite. None of them are meteorites. The surfaces are too rough and, of course, none of them have fusion crusts. If a rock looks like this, then it is not a meteorite.

Meteorites from old, hot deserts

The observant among you may note, “but you have photos of lunar meteorites with rough exteriors on your lunar meteorite website. Correct, but the environmental circumstances are different.

Hot-desert lunar meteorites with rough surfaces. The terrestrial age, if known, is given in yellow.

Nearly all lunar meteorites with rough exteriors were found in hot deserts, mainly northwest Africa (NWA) and Oman (Arabian peninsula). These rocks have been lying on the surface of the desert for tens to hundreds of thousands of years. During that time, they have been “sand blasted” by wind-blown sand, which has removed their fusion crusts and preferentially dug deeper into some places on the exterior of the meteorite than others. Some are pieces of larger meteorites that have simply fallen apart over hundreds of thousands of years, e.g., Dhofar 1085 (Oman) in the upper left.

Here are some other kinds of meteorites with rough surfaces from the Sahara Desert: NWA 11259 |

Few meteorites found in the temperate climates have been exposed at the Earth’s surface for “tens to hundreds of thousands of years” because there are few surfaces that old in, for example, North America or Europe. A meteorite that lands on the surface of Earth gets buried with time (hundreds to thousands of years). Burying a meteorite preserves the fusion crust.

Map of meteorite finds from Roosevelt County, New Mexico. Image credit: Meteoritical Bulletin Database and Google Earth.

The only place in the U.S of which I am aware where meteorites have been found with very old terrestrial ages (50,000-100,000 years) is Roosevelt County, New Mexico. This is a special place where the wind has been blowing the surface soil away faster than new soil accumulates, what geologists call a “blowout area” or “deflation surface.” Between 1968 and 2005, 110 meteorites were found in the area. All are ordinary chondrites except for one ureilite. Most of the rocks have no fusion crust. (I have been unable to find a decent “whole-rock” photo of a Roosevelt County meteorite.) To stress a point I make elsewhere, however, Roosevelt County meteorites are not big rocks. The masses range from 2 g to 8.35 kg, but the median mass (half are smaller, half are larger) is only 25 g, about an ounce.

So, I stick with my story: Unless you found the rock in an old desert, if it has a rough surface with no fusion crust, then almost certainly it is not a meteorite.

Broken meteorites can have rough surfaces

Meteorites do break apart while coming through the atmosphere and after they land. The breakage leads to some rough surfaces, but usually at least one surface is smooth and rounded.

The Ash Creek (L6 chondrite) meteorite was an observed fall in Texas on February 15, 2009. The meteor was captured on video, where it is seen to break apart. Hundreds of small stones have been found around the town of West. Here are 11 of them from the collection of Karl Aston. The stone in the lower left is the most rounded. It has a complete fusion crust and some regmaglypts. Among these stones, it is probably the earliest to have broken off the main mass of the original meteoroid. Several other stones have complete or nearly complete fusion crusts, regmaglypts, and edges rounded by ablation. These stones probably broke from the main mass lower in the atmosphere. The large stone in the middle has a smooth, dark fusion crust on the bottom side that we can’t see, but on top there is a light fusion crust and only a little ablation. This break must have happened at even lower altitude, but still high enough that heating occurred. Finally, some stones have breaks and chips that happened low in the atmosphere or upon hitting the earth. The light-colored interior is visible on these stones. Thanks to Karl Aston for loan of the stones. Photo credit: Randy Korotev