Mining carts appear as light grey and blue, metal, basket-like carts with grey wheels on the bottom.
Most of the time they really serve no purpose other then as art in the level. They can be moved around by pushing them. They will kill small enemies if they happen to land on them, and will not hurt the player if they fall on them or the player touches them when they are moving fast.
They are sometimes used to move or block out harmful objects; the mining carts are the only piece of Equipment that aren't corrupted by the aliens, probably because no use could be found for them.