Meteorite Glossary

Meteorite Glossary

Posted by MikeG on Nov 20th 2022

A Glossary of Meteorite-related Terms used on this Website :

This glossary is for the most-commonly used terms in meteorite collecting, and is not intended to cover all words and scientific terms used in the discussion of meteorites. For a more complete introduction to meteorites, see the article "Meteorites, Ambassadors from Space".

Chondrules - tiny spherical formations of minerals seen only inside some meteorites. These are usually seen as circles in cross-section when a meteorite is cut open. Chondrules can also be seen on the outside of some meteorites, either as flat circles or spheres poking out from the outer surface of the meteorite. Chondrules can be of many colors and sizes. Not all meteorites contain chondrules.

Classified meteorite - this is a meteorite that has been analyzed by a lab and accepted for publication in the Meteoritical Society's official catalogue of meteorites, also known as the "Meteoritical Bulletin". Classified meteorites will always have an official name which is usually determined by the nearest geographical landmark (town, post office, land feature, etc). If the meteorite's original find location is unknown, it is given a catalogue number, such as NWA 869 (which means meteorite #869 that was classified from the region of North West Africa).

Exotic Type - this is a meteorite of a type that is rarely seen and is desired by collectors because of it's scarcity, aesthetics, or scientific significance. There are many different types and sub-types of meteorites, and some are much more rare than others. Exotic types can include planetaries, Vestans, carbonaceous chondrites, and achondrites (brachinites, etc).

Fall - also called a "witnessed fall", is a meteorite whose fall is seen or recorded by eyewitnesses, radar, or cameras. A meteorite fall often becomes a media sensation and is considered more desirable by collectors. An example of a recent witnessed fall is Aguas Zarcas, a meteorite which fell over Costa Rica in April 2019.

Find - a find is a meteorite which was found after it fell (often a long time after it fell). Some finds are accidental, such as when a farmer plows up a buried meteorite in his field. Other finds are intentional, such as when a meteorite hunter searches an area where meteorites have been found previously (such an area is called a "strewnfield"). Gold Basin is a good example of an American find. It is an old chondrite that hails from a strewnfield in rural Arizona and hunters are still finding pieces of it.

Fossil meteorite - this is a very ancient meteorite that has undergone the process of terrestrialization and has lost some of it's character as a meteorite. Such meteorites contain many secondary minerals that are the result of weathering and oxidation. While all meteorites are very old (formed around the same time as our solar system), fossil meteorites have been on Earth for hundreds of thousands of years or millions of years.

Gem jar - a common way to store small meteorites and other specimens. It is a hard, clear, acrylic storage case that is round and usually measures about one inch in diameter. It contains a small piece of foam padding to cradle the specimen and protect it from damage. All gemjars have a removeable lid and an identification label is usually placed inside the gemjar, under the foam padding.

Hammer Fall - this is a witnessed fall where the meteorite(s) struck a man-made object, such as a house, business, or vehicle. If a fall produces many meteorites, only those meteorites which actually struck something man-made are called "hammer stones" or "hammers". A recent hammer fall is Chelyabinsk, which exploded over Russia in 2013, unleashing a shockwave which damaged buildings and injured hundreds of witnesses.

Historical Fall - a witnessed fall that coincides with another event of great significance can be called a historical fall. Or, if the circumstances of the fall are unprecedented or famous in some way, it may also be labelled as a historical. Jilin is called a historical fall because it is the largest single stony meteorite in the world, weighing nearly 4000 pounds. It also showered stones across a populated area, causing a great event as people poured out of homes and schools to look for the freshly-fallen meteorites. Another commonly cited historical fall is Ensisheim, which fell in 1492 and is considered to be the earliest documented and extant meteorite fall.

Inclusion - these are small bodies of material that are embedded into the mass of a host meteorite. Inclusions may be metal, graphite, olivine, silicates, minerals, crystals, or rarely diamond. Some meteorites may contain many inclusions and some may contain none. The type and number of inclusions found in any meteorite varies with the type and individual specimen.

Iron Shale - iron meteorites that have experienced significant oxidation will often deteriorate into fragments of rust flakes called "shale". This is typically seen with ancient iron meteorites (or pallasites) that are now composed almost entirely of rust and rust-related minerals. Such shale still contains traces of the nickel alloys found in meteorites and may contain remnants of the original Widmanstatten pattern.

Meteorwrong - this is any rock or specimen that mimics the appearance of a meteorite. Some terrestrial minerals and man-made materials can resemble meteorites. Common examples of meteorwrongs include hematite, magnetite, and industrial slags.

Micromount - a small sample-sized meteorite specimen. These are also called "thumbnails" by collectors of terrestrial rocks. This is an affordable and modest sized piece that is usually less than one gram. Micromounts of rare types or falls may be measured in milligrams and are sometimes called "Bessey Specks". For a more detailed explanation of micromounts, see the "Micromount FAQ".

NWA meteorite - In the 1990's, a great bounty of meteorites started coming out of the Saharan Desert region of Northwest Africa. Tens of thousands of meteorites, of all types, were brought out of the desert by nomads and then sold to dealers across the world. Most of these meteorites were not collected in the field using scientific techniques and their exact find locations were not recorded. Furthermore, these meteorites changed hands several times before they arrived in labs for analysis. Due to this lack of exact location data, the Meteoritical Society has grouped all of these meteorites together under the "NWA" catalogue name, and each individual meteorite is assigned a number. Currently, there are over 12000 meteorites that are classified as NWA. For a more detailed history of NWA meteorites, see the article "A Brief History of the Saharan Gold Rush."

Peas - are tiny individual meteorites that are about the size of a pea or marble. This is typically seen with stony types of meteorites. Peas are usually small (3g or less), unbroken, and covered in fusion crust. Depending on the type, some meteorite peas are very rare and others are quite common.

Planetary meteorite - a meteorite that originates from a planet or moon in the solar system. Currently there are two accepted types of planetary meteorite - Lunar and Martian. Lunar meteorites originate from our Moon and Martian meteorites come from Mars. There is some scientific speculation that the planet Mercury may be the source of an exotic type of meteorite called "angrite", but this is only a theory and has not been proven.

Riker Box - this is the name for a storage box widely used by meteorite collectors. It comes in a variety of sizes from small to very large. All Riker boxes have some common traits - a glass viewing window in the lid, a black pebble-grain textured finish, white fiber padding, and 2 pins which close the lid to the bottom of the box. Riker boxes are an attractive way to display and store some meteorite specimens.

Scale Cube - the little black cube shown in many meteorite photos, including those on this website. This cube is used by scientists, collectors, and dealers to show scale when photographing meteorites. The cube measures exactly one centimeter on each side. Some scale cubes have markings T,B,N,S,E,W, which correspond to Top, Bottom, North, South, East, and West. These are used to show changes in orientation from one photo to another. Commonly, these cubes are simply used for size comparison, so the buyer of a meteorite knows how big or small the specimen really is.

Shocked meteorite - a shocked meteorite has experienced violent conditions of expansion and contraction due to extreme physical forces. Shock forces are typically generated during impacts in the meteorite's past life in space, or during explosions resulting from atmospheric entry stresses. These meteorites typically have noticeable lines or "veins" inside them that consist of minerals altered by the shock forces. Some meteorites may also contain microscopic or very tiny diamonds which result from graphite inclusions inside the meteorite being compressed into diamonds during extreme shock conditions.

Stable meteorite - some meteorite types (usually irons and pallasites) are susceptible to rusting and other detrimental chemical processes. Exposure to water and chlorine are the most common culprits that will make a meteorite unstable and prone to rusting or deterioration. Meteorites that have never been exposed to such contaminants are often "stable" and will not rot away over time. Rusting or sick meteorites must be stabilized by removing harmful chemicals and moisture - a process which can be very time consuming and labor intensive. Generally-speaking, Earth is a poisonous environment for all meteorites and they will oxidize over time unless they are properly cared for.

Unclassified meteorite - this is a meteorite that has not been officially recognized by the Meteoritical Society. This could mean that the specimen has not been analyzed by a lab, or that the Meteoritical Society never received the required paperwork for publication. Technically-speaking, an unclassified meteorite might not actually be a meteorite, but the majority of unclassified meteorites for sale by dealers have been examined by an experienced eye and determined to be meteorites.

Vestan meteorite - this is a meteorite that originates from the asteroid 4 Vesta in the asteroid belt between Mars and Jupiter. Vesta is one of the largest asteroids in the solar system and it represents a failed planet or "protoplanet". Howardites, Eucrites, Diogenites, and Olivine Diogenites are the major meteorite types that originate from an ancient impact which rocked Vesta and left a large crater that is visible on the asteroid today. These meteorites are also called the "HEDO" class, which is an acronym consisting of the first letter of each Vestan meteorite type. Vestan meteorites often have exotic aesthetics and properties, which makes them highly desired by collectors.