Secondary crust
Secondary crust is a thinner fusion crust formed on surfaces exposed when a meteoroid broke apart late in its flight.
When a meteoroid breaks apart during its bright flight, the new broken surfaces are exposed to the heated air for a shorter time than the original exterior. They form a thinner, less developed crust, called secondary crust. If a break happens very late, close to the end of the luminous phase, the new surface may form only a very thin film or no crust at all.
Looking at a meteorite's crust can therefore reveal its history. A stone may have a thick, primary crust on some faces and thin secondary crust on others, showing where it broke during descent. Faces with no crust at all usually broke after landing, perhaps on hitting rock or during recovery.
Scientists and hunters use these clues to fit fragments together and reconstruct how the meteoroid fragmented. It also helps confirm that broken surfaces are genuine, rather than damage from handling or deliberate cutting.
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