alot of the flying rocks of pandora eerrr the mistlands do that. thats why i refer to them as such. ancient armor mistland rocks and mistlands blue lantern posts ALL float. they dont fall..
same for petrified bones. tho these will crumble if enough total dmg was dealt to it but mineing them out is PAIN because of them likeing to stay floaty.

i hope the devs address some of this. the game simply doesnt regognize some of these objects in the air correctly currently and its only in the mistlands biome. thats because they all have 1 thing in common : all are NEW ASSETS. so this is simply a bug on these assets that needs to be fixed sooner or later. granted its not a critical bug.

but dont build your base on a floating lanternpost. otherwise a future patch WILL make your base crumble to dust.

i guess the new patch might fix some of these hopefully.

i just had an ancient armor floating in mid air over ocean water yesterday. RIP ironscrap. all feel into the sea.

The dwarven outposts if you destroy the bottom (I use a 2h hammer) it will float in the air. (I use these to get black marble) When its floating in the air, there are wood beams. I hit those with the fire staff and the entire thing comes falling down. For some reason their wood beams in the stone are super strong hehe.

Wood constructions can also float in the air without a connection (depending on how high you built them and what size parts you used).

The silo I built at this base was for decoration until I could build a windmill. I used the shortest wall pieces and I removed the entire lower level of walls and it didn't start collapsing until I removed the 2nd lowest level of walls.
https://steamcommunity.com/sharedfiles/filedetails/?id=2853688746

Ore nodes will float in the air if you dig out around them until the soil is too far away or until you strike the node in the exact center (assuming you have cleared away all the soil) at which time it will shatter into a shower of ore and stone.
https://steamcommunity.com/sharedfiles/filedetails/?id=2856429325
If you dig around large boulders they will sink (and if you fill in terrain around them again they will pop back up. You can't bury them).

Actual terrain doesn't move when you dig on it or under it so you don't need timbers to support a tunnel and its possible to dig so that you have a patch of dirt floating in the air.

The large flat stones in the plains and black forest that look like copper deposits behave like terrain.

For rocks/ore deposits there is a large invisible space around each node, which if it collides with another objects invisible space will prevent collapse. There was a mod somewhere which used wireframes to show the nodes actual collisions, and even suggest which piece is preventing collapse - I've completely forgotten what it was called though.

Hmm, I just cut out the bottom of an ore node and it collapsed as expected. I will have to try a rock/boulder to see if the same thing happens.

had a lot experiments going on in the past
there are some elements in game just floating like the statues from the swamps

Here - and although you can't see it, that tree isn't touching the outcrop.

https://steamcommunity.com/sharedfiles/filedetails/?id=2925465394

looks like that object does not have any "physics" like some other have
hard to say
there are circumstances where i managed to have floating structures when i clipped a lot of parts in

maybe the devs may have a look at this.

Originally posted by Mr B.:

Here - and although you can't see it, that tree isn't touching the outcrop.

https://steamcommunity.com/sharedfiles/filedetails/?id=2925465394

This happens to me with copper sometimes