Merrillite
Merrillite is a calcium phosphate mineral common in meteorites and lunar rocks but almost unknown on Earth.
Merrillite is a calcium phosphate with magnesium and sodium, closely related to the terrestrial mineral whitlockite but containing no hydrogen. It was named after George P. Merrill, an American meteorite researcher.
Merrillite is one of the most common phosphate minerals in meteorites. It occurs as small grains in ordinary chondrites, especially those heated to petrologic types 5 and 6, as well as in eucrites, Martian meteorites, mesosiderites and lunar rocks. Its lack of hydrogen reflects the dry conditions in which these rocks formed or were reheated.
Merrillite is valuable because it concentrates rare earth elements, uranium and thorium. That makes it useful for radiometric dating and for tracing how a body's magma evolved. In Martian rocks, merrillite and its neighbour apatite help scientists estimate how much water and chlorine Martian magmas contained.
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