Can You Identify Which Rock Is a Meteorite
Hardly a day goes by when we don’t receive emails from people who think they’ve found a meteorite. With this in mind we wrote a chapter in our new book “Meteorites – How To Recognize Visitors From Space” on how to identify meteorites. Below is the chapter from our new eBook.
Meteorite or Meteor Wrong
The Side by Side Test
Meteorite hunters have created a funny term to refer to all the many rocks that look similar to meteorites but are not, they call them meteor “wrongs”.
One meteorite testing laboratory a few years ago said that they received on average 7000 rock samples per year from persons who thought they had found a meteorite. On average there were only one or two real meteorites per year. With the wonderful media attention meteorite hunting has gotten in the last three or four years that facility had to stop accepting samples because they could no longer handle the demand. It is hoped that with the help of this book and its photographs the number of real meteorites sent to laboratories will go way up.
Nothing beats a step by step tutorial for learning new things. So here is a test on two stones that look very similar. One is a meteorite and one is not. Much more will be said later about the characteristics seen in the photographs.
Both stones pictured above are about the same color and size. They are both the correct color for a possible meteorite. Both are a shape that a stone meteorite could certainly have. The texture on the surface is within the range that a meteorite might display. The stone on the left is 9 grams and the one on the right is 6.9 grams in weight.
Both of the stones will hold a magnet. So, both are somehow related to iron in their composition. The next step in testing, whether it is done at home or in the field while hunting, is to try and peek at the insides. You want to grind off with a diamond file a small spot. If it is a meteorite you will be happy that you did as little damage as possible.
Here are those spots after grinding. You will want to note the color of the powder the file creates. It can often be an immediate tip-off to several of the common iron minerals you will encounter.
Here you can see that there are no features in the rock on the left at all. It is a nodule of some iron mineral. The rock on the right however, shows many small grains of iron and several small chondrules which will be discussed at length later. The rock on the right is the meteorite. What was the rock on the left? As the next two photographs will show, the color of the powder from filing the stone holds the answer.
Just as in the normal streak test done on minerals red is the color which hematite produces. Hematite is the highest grade iron ore and is often found as small nodules while hunting meteorites. While it may not always stick to a magnet many times it does. The red powder from Hematite has been used throughout human history as a color pigment. It is the rouge red of yes, rouge. Mixed with animal fat or water it was the coloring for cave paintings. But, it is the wrong color for the mineral powder of meteorites.
Here is the powder from the meteorite stone. It will almost always be a brown with an older stone. The other most common mineral that you will find sticking to your magnet while hunting is Magnetite. It will make black colored powder and the stone will be black as well. It will often show flat crystal surfaces with dull black luster when found in nodules. These two iron minerals make up a major portion of the meteor wrongs.
It will not be discussed much later so this is a good time to mention a few other things that real meteorites will not display. Meteorites are not porous like lava rocks. With only a handful of exceptions meteorites are solid inside. Though old ones may have microscopic cavities where iron grains have rusted out, the remaining iron will be a positive sign it is a meteorite anyway. So if it has big cavities or is just bubbly, it is not a meteorite. My first find as a kid was a piece of basalt. Which I was sure was a meteorite. I eagerly sent it to the famous “Father of Meteoritics” Dr. Nininger. He sent me a nice post card back saying you have a plain old piece of lava rock. I was pretty devastated. But, a few days later I got a letter with some pages of material describing real meteorites and what they look like. Thus began the journey of a lifetime into the world of meteorites.
Meteorites do not have quartz in them. Quartz and calcite are the two most common crystals seen while out hunting rocks. Meteorites do not have shiny crystal surfaces like terrestrial rocks. Some meteorites do have crystals but the presence of a lot of iron will make them obvious meteorites.
Meteorites do not have layers of minerals in them. One of the common “hot rock” types is gneiss with magnetite seen in layers of black running through the stone. Small pieces of this gneiss will stick to a magnet and also illicit a response from a metal detector. Sometime the pieces of these gneisses and granites will create a signal nearly as strong as a low metal meteorite might create. Here is where practice and persistence come in.
Author: James Tobin [Google]
We hope you enjoyed this chapter on meteorite identification and if you’ve ever thought you would like to hunt for meteorites, are a meteorite collector with some unclassified meteorites, or you just want to know more about meteorites this book will help.
Packed with photos and practical information even the seasoned meteorite collector and hunter will enjoy the stories and close up meteorite photography. You can read the reviews and purchase on Amazon by clicking on the book cover below.