maskelynite

Maskelynite is a glassy material found in some meteorites and meteorite impact craters. Typical samples are similar in composition to plagioclase feldspar, and revert to that mineral when melted and recrystallized. It was named after British geologist M.H.N. Story-Maskelyne.

Since maskelynite (like the volcanic glass obsidian) lacks an orderly arrangement of atoms, it is not considered a "mineral" by geologists, and is not listed as such by the Mineralogical Society of America.