Flow lines

Some few meteorites have "flow lines" but so do terrestrial rocks, both natural and man-made

Northwest Africa 2998 is an “oriented” meteorite. It came through the atmosphere without tumbling front to back. Melt formed on the leading edge and flowed toward the trailing edge during its entire entry. Oriented meteorites frequently have a rounded, conical leading edge. Fusion crust covers the whole meteorite, however, except where it has chipped off since landing on Earth. Feldspathic lunar meteorites like NWA 2998 have lighter-colored fusion crusts than do ordinary chondrites, but where it has chipped off, the interior is even lighter colored. This characteristic is typical of nearly all meteorites and is one of the reasons I say below that none of the rocks in the mosaic has a fusion crust.

Many people have told me that they think their rock is a meteorite because it has “flow lines.” Few meteorites have flow lines.

Flow lines and other flow-like features are common on meteorwrongs, however. The photos below were all sent to me by persons who enquired whether the object was a meteorite. Note that none of the objects has a fusion crust.

This is simple: If a rock does not have a fusion crust, then it does not, and cannot, have meteorite flow lines.

Note that none of these apparent flow features is on a “nose cone;” they are on flat parts. Most of these things are industrial slag – once molten stuff that was so viscous that flow features froze as the liquid cooled. Flow features do occur on terrestrial basalts, however. For reasons I do not understand, some hematite concretions have flow-like features, although they were never molten.