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Chondrite is a scientific term for a meteorite that has not been altered in size, shape or composition due to entering the earth's atmosphere. When the materials of a meteorite have not been separated or melted because of the extreme heat they are subjected to upon entry, the remaining rock is termed a chondrite meteorite. These meteorites account for approximately 86 percent of all meteoric material recovered from the Earth's surface. Meteorites that do not contain “chrondules,”or grain-like drops of formerly molten material, are thought to have made up the basis of our solar system. Chondrules assimilate into meteorites; meteorites without chondrules are termed “achondrites.”
Chondrites are separated into 15 distinct groups that are classified based upon their chemical composition. Common chondrite identification usually falls within one of three groups: ordinary chondrite, carbonaceous chondrite and enstatite chondrite. Ordinary chondrite specimens account for 90 percent of all finds. Carbonaceous chondrites make up less than 5 percent of all chondrites found, and enstatite chondrite materials comprise less than 2 percent of all finds.
Ordinary chondrites contain numerous chondrules and variable amounts of metals. Ordinary chondrite materials are separated further into three categories: high iron content, low iron content and low metal and iron content. About half of all ordinary chondrites found on earth are of the L type, or low iron content type. Approximately 40 percent are of the H type, or high iron content variety. The remainder of ordinary chondrites are made of the rare LL, or low metal and low iron type.
Carbonaceous chondrites contain refractory elements, which shine or sparkle when exposed to light. They contain varying amounts of chondrules, and are classified based upon the amount and type of metals they contain. They are also classified further based upon the amount of refractory material they possess.
Enstatite chondrites are different from their cousins in that the metals that compose them are almost always reduced in some form. For example, most enstatite chondrites contain a great amount of iron. Instead of metal or sulfide form, the iron contained within enstatite chondrite meteorites is almost always in iron oxide form.
In addition to rare metals, common metals and refractory materials, chondrites are often embedded with grains of material that pre-date the formation of the solar system. These are of particular interest to astronomers and scientists who wish to know about the formation of our solar system, galaxy and the earth. It is estimated that there are approximately 27,000 chondrites in the world's scientific and public collections, as well as many more in the hands of private citizens.