The Fukang meteorite is a meteorite that was found in the mountains near Fukang, China in 2000. It is a pallasite—a type of stony–iron meteorite with striking olivine crystals.This information from the Reddit discussion thread:
The pattern, called a Widmanstätten pattern, is due to what is called subsolidus exsolution. Iron meteorites will crystallize as a mineral called taenite. Once the mass is cooled and if it is cooled slowly enough, kamacite and taenite will form. The cool thing to realize is that this is done very slowly and all while solid! No melting is taking place... Meteorites just have stupidly slow cool down rates since the vacuum of space make an awesome insulator.Photo from imgur, where the title pun is repeated ad nauseum (but it serves as a good way to remember the identity of the material).