Fossils randomly generate y-coordinates 40 to 49 underground in the Overworld (deserts, swamps, and their variants). Each chunk has a 1⁄64 chance to generate a fossil. They may generate as one of the four variants of skull or one of the four variants of spine.
Fossils first generate the pure-bone block fossil with a structure integrity of 0.9, meaning 10% of blocks are replaced with structure voids. Next, the coal fossil generates with a structure integrity of 0.1.
In Java Edition 1.17[upcoming], fossil generation has changed. There are now two types of fossils, each having a 1⁄64 chance to generate per chunk. One fossil generates between levels 0 and 320. Another generates from level -63 to -8, and is composed of diamond ores as opposed to coal ore.
Note that naturally generated fossils are composed of a mix of bone blocks, coal or diamond ores, and structure voids, as detailed above. They are made with the NBT structure block format and have NBT files for each type of fossil located in the folder
|Structure name||Description||Consists of||Image|
|skull_1||The largest skull.||86 Bone Block|
|skull_1_coal||Skull_1 being petrified.||86 Coal Ore|
|skull_2||The second largest skull.||75 Bone Block|
|skull_2_coal||Skull_2 being petrified.||75 Coal Ore|
|skull_3||The second smallest skull.||58 Bone Block|
|skull_3_coal||Skull_3 being petrified.||58 Coal Ore|
|skull_4||The smallest skull, one-eyed.||32 Bone Block|
|skull_4_coal||Skull_4 being petrified.||32 Coal Ore|
|spine_1||The narrowest spine.||37 Bone Block|
|spine_1_coal||Spine_1 being petrified.||37 Coal Ore|
|spine_2||The second narrowest spine.||61 Bone Block|
|spine_2_coal||Spine_2 being petrified.||61 Coal Ore|
|spine_3||The second widest spine.||97 Bone Block|
|spine_3_coal||Spine_3 being petrified.||97 Coal Ore|
|spine_4||The widest spine.||121 Bone Block|
|spine_4_coal||Spine_4 being petrified.||121 Coal Ore|
|May 13, 2016||ProfMobius tweets an image of the new structure blocks in action, generating what appears to be a fossil made of quartz.|
|Upcoming Java Edition|
|1.17||21w10a||Fossils that generate below Y=0 now generate with either normal or deepslate diamond ore instead of coal ore.|
|Fossils can no longer generate in the air.|
|1.1.3||alpha 22.214.171.124||Added fossils.|
|Legacy Console Edition|
|TU43||CU33||1.36||Patch 13||1.0.1||Added fossils.|
|New Nintendo 3DS Edition|
- Coal ore generating among fossils could be based on the common misconception that coal and other fossil fuels are formed from fossilized animal remains. While coal can indeed originate from and around fossils, it is usually those of plants and plant matter.
- Diamond ore generating in place of coal ore in fossils below y=0 could also reflect the common misconception that diamond is formed from highly compressed coal; diamond is in reality a pure carbon allotrope dating back millions of years before the first coal appeared, as coal is formed from decayed plant matter.
- Hidden in the structure NBT is data that credits ProfMobius with the creation of the fossils.
Fossil generated on a superflat world. Some bone blocks are removed/replaced with coal ores.
A fossil that has generated underwater, inside an underwater ravine.