Fossil

A fossil is a rarely-occurring skeletal feature composed of bone blocks, coal ore above Y=0, or diamond ore below Y=-8.

Fossils randomly generate only in desert, swamp and mangrove swamp biomes. Each chunk has two attempts within Y-coordinates 0 to 320 or -63 to -8 underground to generate a fossil, each with a chance of 1⁄64. They have an equal chance to generate as any of the four variants of skull or four variants of spine.

Fossils first generate the pure-bone layer with a structure integrity of 0.9, meaning 10% of the bone blocks are removed and do not override original terrain blocks, leaving 90% bone blocks. Next, the ore layer generates with a structure integrity of 0.1, replacing 10% of the existing fossil with coal ore for fossils that generate above Y level 0. Diamond ore or deepslate diamond ore generate below Y level -8. The locations of these ore blocks do not always correspond with the voids generated in the initial bone fossil, so the resulting combination of both generations usually result in an incomplete fossil structure composed of bone blocks and ores.