How to Identify Meteorites
Think you have a meteorite? Meteorites have several distinguishing characteristics that make them different from terrestrial (Earth) rocks. Sometimes detailed chemical analysis are required to identify meteorites; however, most of the time, you can identify a meteorite by recognizing the following characteristics: fushion crust, density, magnetism, iron-nickel metal, regmaglypts, and chondrules.
Before getting too excited, two characteristics must be observed in the rock to identify it as a meteorite: streak color and magnetism.
Magnetism is fairly easy to test. Just find yourself a good, strong magnet. Meteorites generally have strong magnetism. Another characteristic to observe is the streak color. In order to determine the streak color, simply find a porcelain plate that has a "dull side" to it. With medium force, rub the rock across the dull side of the plate. If after testing the streak color, it fails to leave a streak behind, then the rock could possibly be a meteorite. Often times, magnetite and hematite rocks are misidentified as meteorites. This is because they look similar to meteorites and they have higher densities than other non-ore rocks. Magnetite, which has magnetic properties will give a silver-gray color for its streak, while hematite with little to no magnetic properties will give a deep red color. If the rock has a strong magnetism with no streak color, and it has a high density (weight per volume ratio), you may just have yourself a meteorite. Another characteristic to look for is the presence of regmaglypts.
Before getting too excited, two characteristics must be observed in the rock to identify it as a meteorite: streak color and magnetism.
Magnetism is fairly easy to test. Just find yourself a good, strong magnet. Meteorites generally have strong magnetism. Another characteristic to observe is the streak color. In order to determine the streak color, simply find a porcelain plate that has a "dull side" to it. With medium force, rub the rock across the dull side of the plate. If after testing the streak color, it fails to leave a streak behind, then the rock could possibly be a meteorite. Often times, magnetite and hematite rocks are misidentified as meteorites. This is because they look similar to meteorites and they have higher densities than other non-ore rocks. Magnetite, which has magnetic properties will give a silver-gray color for its streak, while hematite with little to no magnetic properties will give a deep red color. If the rock has a strong magnetism with no streak color, and it has a high density (weight per volume ratio), you may just have yourself a meteorite. Another characteristic to look for is the presence of regmaglypts.
What are Regmaglypts?
Regmaglypts are thumb-like impressions that appear on the surface of meteorites. Such phenomena forms as the meteorite passes through the Earth's atmosphere.
Notice that this meteorite has a red color to it. Meteorites can come in an assortment of colors, but generally they are of the gray, gray-black, brown, and red colors.
Unlike iron meteorites (left photo), stony meteorites contain chondrules. Chondrules are tiny mineral beads with spherical bodies that represent partially melted material in a rocky matrix. Chondrules represent the oldest known materials within our solar system. They are thought to have formed from the condensation of hot gasses in the early formation of our solar system.
Notice that this meteorite has a red color to it. Meteorites can come in an assortment of colors, but generally they are of the gray, gray-black, brown, and red colors.
Unlike iron meteorites (left photo), stony meteorites contain chondrules. Chondrules are tiny mineral beads with spherical bodies that represent partially melted material in a rocky matrix. Chondrules represent the oldest known materials within our solar system. They are thought to have formed from the condensation of hot gasses in the early formation of our solar system.
Stony Meteorites
The largest group of meteorites are the stony meteorites. Many such meteorites have been on our planet's surface for an extended period of time; therefore, they frequently look very much like terrestrial (Earth) rocks. However, when sliced opened and polished, one can clearly see the chondrules which were accreted together to form the meteorite. Iron meteorites, like the upper two photos were once part of the core of a long-vanished planet or large asteroid and are believed to have originated from the Asteroid Belt which is located between the two planets Mars and Juipiter. To learn more about asteroids and other space objects, check out the "Space Wonders" tab provided on this website.
A Work of Art!
Thin sections made from meteorites can be used to classify whether a rock is a stony or iron-nickel meteorite. By using transmitted polarized light, with a red-quartz filter, crystals of olivine (bright colors) and pyroxene (gray colors) are visible in this stony meteorite. Credit for photo: Bob King.
Stony meteorites have porphyritic texture. Porphyritic texture is a term used for igneous rocks that display large crystals embedded within a finer groundmass (matrix). Any rock possessing porphyritic texture, has obvisouly undergone at least two different phases of cooling.
Stony meteorites have porphyritic texture. Porphyritic texture is a term used for igneous rocks that display large crystals embedded within a finer groundmass (matrix). Any rock possessing porphyritic texture, has obvisouly undergone at least two different phases of cooling.
What are Tektites?
Tektites are natural glass objects, primarily composed of silica, that have formed on the Earth by a large asteroid or cometary impact. The energy from the impact melts the terrestrial (Earth) rock and ejects it up into the higher elevations of the atmosphere. A few minutes after the impact, the tektites rain back down onto the Earth, and as they are falling, they can take on a number of morphological shapes as they are cooling. There is still some debate as to how these unique rocks formed, however, most scientists agree that they were formed as the result of a large asteroid or cometary impact.
Assortment of Tektites:
As you can see, tektites can form in a variety of shapes and sizes. They can take on a teardrop, oval, hamburger patty, sphere, dumbbell, and hollow-centered ball shape. Depending upon their spin as they re-enter the lower atmosphere, the friction in the air deforms the glass material, thus giving them their unique shapes and sizes. Tektites resemble volcanic obsidian. Obsidian is a hard, usually black volcanic rock made entirely of glass. Obsidian cools very fast when hot lava material flows across the surface of the Earth and solidifies.
Moldavites:
Moldavites, a form of tektites, are of the olive green or dull greenish color. They are generally translucent and have a vitreous (glassy) luster. Because of their beauty and rarity, they are sometimes cut and polished into ornamental stones named pseudo-chrysolites. Moldavites are believed to form the same way as do regular tektites. So what makes moldavites green? Iron is responsible for giving the moldavites their pretty green color. Like tektites and obsidians, moldavites are brittle and break off into ring-like shapes or have curved breakage called chonchoidal fracture. Broken glass bottles also display this same type of fracture.