The objective of this work is the separation of paramagnetic particles by a high gradient magnetic separator (HGMS) out of the calcium carbonate slurry, which is traded as a filler material and surface coating pigment into the paper industry. For the testing series, conducted to systematically optimise the operation parameters of the super conducting magnetic separation, a Carpco pilot plant was installed into the production process onsite. As the efficiency criteria of the HGMS-process the whiteness (tappi) and the yellowness (index) of the purified slurry were measured over the production time and compared with the feed properties. Basic influence parameters of the separation by means of a superconducting magnetic separator are the production time per cycle, the fineness of the used matrix pads, the magnetic flux density, the slurry velocity of the feed and the effect of the flushing and rinse velocity during the regeneration of the matrix which was optimised continuously. A long time test could verify the results from the parameter study. Additionally the possibility of a simple production control by measuring the matrix differential pressure during the production cycle was investigated.