A calibration assembly is disclosed. In one embodiment, a calibration assembly calibrating a downhole formation evaluation tool includes a calibration base having a first geometry, a calibration insert including a first material and having a second geometry, and a second material having a third geometry and being different from the first material. The second geometry enables the calibration insert to receive the second material to form a first composite region, wherein the first and second materials and the second and third geometries are selected such that a calibration property of the calibration assembly apparatus substantially matches a corresponding calibration property of a third material. Additional apparatuses, devices, and methods are also disclosed.