One quirk of the system is that floating objects can support each other.

Example: mining brain tissue in mistlands, excavating a skull from the mountainside - One rocky extrusion was still poking into the skull, despite both the skull and this rock having no connection to the ground. As soon as i found and broke that bit of rock, the whole skull fell to pieces.

Another example i've come across is silver veins intersecting. Even after i'd totally excavated both, neither would collapse, until i mined out the area where they touched each other.