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 by structure voids, leaving 90% bone blocks. Next, the coal fossil generates with a structure integrity of 0.1, with 90% of the fossil blocks are replaced by voids, leaving 10% coal. The locations of coal blocks do not always correspond with the voids generated in the bone fossil, so the resulting combination of both generations combine to make an incomplete fossil structure composed of bone blocks, coal, and structure voids.
In Java Edition 1.18[upcoming], there are two types of fossils, each having a 1⁄64 chance to generate per chunk. One fossil generates with coal ore between levels 0 and 320. Another with diamond ore rather than coal ore generates from level -63 to -8.
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.|
|September 28, 2019||Prerelease footage of the soul sand valley biome at MINECON Live 2019 appears to have used these fossils (as opposed to the distinct nether fossils).|
|1.16||20w22a||Fossils can no longer overwrite desert pyramids or the end portal room of strongholds.|
|1.17||21w06a||Fossils can now generate in the air due to a bug.|
|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.|
|21w15a||Because world generation has been reverted, fossils generate the way they did before the 1.17 snapshots.|
|Upcoming Java Edition|
|1.18||Experimental Snapshot 1||The fossil generation changes in the 1.17 snapshots have been reintroduced.|
|experimental snapshot 5||Fossils with diamond ore no longer generate above the deepslate level.|
|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|
- 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.
- – "Fossils can generate floating in caves" – resolved as "Fixed"