SiO2-rich condrules in ordinary chondrites

The solar system abundances of Mg, Fe, and Si dictate that chondritic meteorites are silica-deficient compared to most terrestrial or lunar igneous rocks; thus olivine-orthopyroxene assemblages are commonly observed in ordinary chondrites. However, in the unequilibrated H-chondrites Sharps, Bremervorde, and Dhajala, we have observed chondrules and fragments which contain either tridymite or cristobalite as a major phase.