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The chondrites of this clan are designated as “ordinary” just because they represent the most common class of stony meteorites on Earth, accounting for more than 85% of all witnessed meteorite falls. But as genuine pieces of primordial matter, ordinary chondrites are everything else but ordinary since they are more rare than gold or diamonds and – with crystallization ages of about 4.5 billion years – much older than any rock or mineral known on our planet.
More importantly, ordinary chondrites might not be that common at all when it comes to the actual distribution of chondritic matter in our solar system. Some researchers have suggested that the high percentage of ordinary chondrite falls might only be due to the coincidence of the crossing orbits of certain near-Earth asteroids – the so-called NEOs – and the orbit of the Earth. If the majority of those NEOs would be of ordinary chondritic composition this would of course result in a higher percentage of ordinary chondrite falls. Thus, ordinary chondrites might be not that ordinary at all.
In terms of mineralogy, all ordinary chondrites are composed of olivine, orthopyroxene, and a certain percentage of more or less oxidized nickel-iron. Based on the differing content of metal and differing mineralogical compositions the ordinary chondrites have been subdivided into three distinct groups that are designated as H, L, and LL chondrites.
Learn more about the different types of ordinary chondrites – just follow the respective links.