Disclosed is an apparatus for mixing laboratory vessel contents. The apparatus has an accommodating adapter with a holder for accommodating laboratory vessels, e.g., laboratory vessels in an exchangeable block module, and a drive for putting the accommodating adapter into a mixing movement which essentially oscillates in a circular and translatory manner in a horizontal plane. The accommodating adapter has a vortex adapter which is accessible from the outside and has a shoulder structure on a circumference. The shoulder structure has at least one shoulder which points toward the center of the circumference and is intended to drive a vessel, e.g., a test tube, which is held and placed from the outside, into the mixing movement in a form-fitting manner.