Rollover lip
A rollover lip is a rim of melted crust that flowed over the edge onto the back of an oriented meteorite.
An oriented meteorite is one that kept a stable position as it fell, like a badminton shuttlecock, rather than tumbling. Its front became smoothly rounded and its back flatter. During flight, molten crust flowed from the front towards the edges. At the rim, some of it spilled over onto the back surface and froze, forming a ridge called a rollover lip.
Rollover lips are a sign of a well-oriented specimen and are especially prized by collectors. They show the direction of airflow and confirm which side faced forwards. They often appear together with radiating flow lines on the front and a rougher, thicker crust on the back.
Oriented meteorites with good rollover lips are uncommon, perhaps a few per cent of stones from a fall. Examples are known from falls such as Sikhote-Alin for irons, and from many stony meteorites, including some recovered from desert strewn fields.
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