The Department of Earth Sciences has a few faculty members who provide outreach in the form of rock and meteorite identification. However, we have been receiving a multitude of rock and meteorite identification requests and are not able to respond to all inquiries in a timely manner due to limited time and resources. If you believe that you have a meteorite, please read through the information below to help you gather more information about your rock.
What is a meteoroid, meteor, and/or meteorite?
A: A meteoroid is a rock in space that has not entered the Earth’s atmosphere and is orbiting around the sun. As it enters or passes through the Earth’s atmosphere, it creates light that is visible from Earth. Pebble and smaller sized objects produce a streak of light across the sky as they burn up and are called meteors. The parts of larger objects that survive passage through the atmosphere and land on Earth as solid objects are referred to as meteorites.
You found an interesting rock, is it a meteorite?
A: The most realistic answer is probably not. Statistically speaking it is highly unlikely to stumble upon a meteorite. Minnesota has an amazing geological history which has left us with a lot of rocks that are very interesting to look at, but finding a meteorite in Minnesota is highly unusual. Most meteorites are found in deserts and Antarctica because they are easier to differentiate from the sand and ice that dominates those landscapes. With the wide diversity of rocks that Minnesota is home to, locating a meteorite extremely unlikely. Less than one in 1000 of the objects brought to the University for identification have proven to be meteorites.
“But I saw it fall from the sky”. There are many reasons that rocks may appear to fall from the sky. Not every rock that appears to fall from the sky out of nowhere is a meteorite. There have been plenty of instances where rocks have “fallen” from the sky due to a variety of human activity. Check out some examples here.
Is it magnetic?
A: Most Meteorites will attract cheaper magnets because they contain iron-nickel metal. Many terrestrial rocks can be magnetic as well, but testing the rock to find out if it is magnetic is the first step.
Does it have vesicles (holes) or is it layered?
A: Vesicles are small cavities or holes found in igneous rocks that are formed by the expansion of gas or steam when rock formed by molten magma cools and solidifies as a lava flow. Meteorites generally do not have vesicles because most meteorites were never in a molten state. By contrast, Minnesota has many ancient lava flows that are over 1 billion years old, and many of these contain vesicles. Sometimes these small holes have been filled with secondary minerals like quartz and calcite. If your rock has vesicles, then it is most likely not a meteorite, but rather a terrestrial igneous rock (like volcanic rock) formed by the wonderful mechanics of the Earth’s systems.
If your rock has distinct layers, it is not a meteorite. Many of the magnetic, dense rocks found in Minnesota are pieces of the Banded Iron Formations from northern Minnesota and are layered sedimentary rocks. These are the rocks that have been important to the mining industry in northeastern Minnesota.
Could it be industrial slag?
A: Slag is a glass-like by-product left over after metal has been separated from its raw ore and is also produced in coal fired furnaces and engines -- the old steam engine powered trains, boats, threshers, saw mills, etc and in current coal fired power plants. Slag will often retain some of the metal after the metal-ore separation process, and thus can occasionally be magnetic. Slag may also appear to have glassy surfaces and it is common that they have vesicles (gas bubble holes). Slag can often be mistaken for a meteorite because of its interesting structures and morphologies.
Slag can be more commonly found in Minnesota due to the iron ranges in the northeastern part of the state and the companies that process Minnesota iron ore.
Is it heavy for its size?
A: The most common meteorites contain iron-nickel metal, which makes them more dense than most rocks found on Earth. However, there can be terrestrial rocks that are very dense for their size.
Try finding a variety of terrestrial rocks of a similar size to feel for any major weight differences. If your rock feels extremely heavy for its size, then it may be a meteorite, but weight and density does not strictly define a meteorite.
Does it have a fusion crust?
A: A fusion crust is formed upon entry to the atmosphere. When a Meteoroid (a) enters the atmosphere, the air in its path heats to extreme temperatures, which causes the exterior of stony meteoroids to melt and ablate (slide off). This continues until the meteoroid slows down enough that the last bit of exposed material to melt will cool to make a thin, glassy coating called a fusion crust. Fusion crusts are seldom more than 1 or 2 mm thick and not distinctly vesicular (bubbly). Fusion crusts have a dull, “matte” appearance -- they are not shiny.
Many terrestrial rocks may develop weathering crusts, rinds or coatings due to numerous processes on Earth, such as chemical weathering or biological activity. Some of these crusts, rinds or coatings can mimic a meteorite fusion crust, but if the coating is relatively thick (more than 2mm) and/or the outside crust is the same color as the inside, it is probably not a meteorite.
Does it have regmaglypts?
A: Not to be confused with vesicles, regmaglypts are small, shallow indentations that may resemble something similar to a thumbprint in a piece of clay. They are more common on larger meteorites and are created during the ablation process (rock surface-melting process) that takes place when a meteoroid travels through the Earth’s atmosphere.
Please keep in mind that many terrestrial rocks can show similar formations due to weathering, erosion, and rock formation processes.
What are the next steps?
A: Hopefully this information helped you to learn more about the rock you have. If your rock appears to have regmaglypts and a fusion crust, then it very well maybe a meteorite and we would be happy to help you identify it. If your rock doesn’t have these items, but you are still sure that it is a meteorite, we are still happy to help you identify it.
To start the process of meteorite identification with one of our faculty members, please send us 3-5 clear pictures of the rock (including different angles and sides) with a detailed description from the information you learn about your rock from above to firstname.lastname@example.org. Please be sure to include a picture of the rock next to a coin or a ruler to show the size of the rock. If your pictures are not clear or you do not provide enough information, we will not be able to begin the process of identifying the item.
Once we have received your email with the necessary information, we will pass it along to one of our few faculty members who work with the public to identify meteorites. Please keep in mind that these faculty members are first and foremost professors and researchers who have very busy schedules including teaching, research and fieldwork. This means that they may take longer to respond to inquiries and will only be able to provide outreach when available.
It is important to know that it is nearly impossible to identify a meteorite from just looking at it so please be prepared to send in a sample if necessary.
Please DO NOT simply “drop in” to the department with the expectations of having a rock identified at that moment. It is extremely rare that we will have one of the few faculty members who work with meteorites available to meet with you and we do not want you to feel that you have wasted your time. Remember that it is best to begin by sending us information and pictures of the rock via email and let us take it from there.
If you have any further questions, please call 612-624-1333 to speak with the front desk.