CH chondrite
CH chondrites are metal-rich carbonaceous chondrites dominated by tiny chondrules and fragments, with very little matrix.
The CH chondrites are an unusual group whose name means "high metal" rather than referring to a type locality. The first recognised member was Allan Hills 85085, found in Antarctica. CH chondrites contain abundant iron-nickel metal, much of it chemically zoned in a way that implies condensation from hot gas, alongside very small chondrules and chondrule fragments, often only tens of micrometres across. Most chondrules are cryptocrystalline or skeletal, many lack the iron-poor and iron-rich spread seen in other groups, and the fine-grained matrix is scarce, occurring mainly as hydrated clasts.
CHs belong to the CR clan, sharing oxygen and nitrogen isotope characteristics with the CR and CB groups. Their unusual components have been interpreted as products of a gas–melt plume generated by a large collision between planetary embryos, mixed with more normal nebular material; some of their CAIs, by contrast, seem pristine. They are therefore important in debates about whether some chondrules formed by impacts rather than by nebular processes.
CHs are known almost entirely as finds from Antarctica and hot deserts such as the Sahara. Recognition depends on texture under the microscope, metal abundance and composition, and bulk oxygen isotopes.
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