Needles

If it contains large needle-like features, then it is not a meteorite.

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In a meteorite, it is rare to find any linear crystal or clast that is 1 millimeter or greater in length and has an aspect ratio (length/width) greater than about 3. If there are lots of needle-like features, then the rock is very probably not a meteorite. Geologists would call such rocks acicular.

All of the photos below were sent to me by persons asking whether the rock was a meteorite. None of them are meteorites. Note that none of the rocks has a fusion crust.

These rocks are not meteorites. Most are terrestrial volcanic rocks with acicular (needle-like) mineral grains.

Exception

A sawn face of Erg Chech 002, a rare ungrouped achondrite (igneous rock). Among meteorites, this is the most blatant exception to “no needle-like crystals” guideline of which I am aware. Photo credit: Chen Wang

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