The calcium-containing compound used is the product anhydrite Trefil 1313-100 with x50.3 = 6.8µm from Quarzwerke GmbH (Frechen, Germany). Trefil consists of 98.4% calcium sulphate by mass and is therefore a mineral that is suitable for dissolving Ca 2+ ions. Talc EX-GT-10 with x50.3 = 5.7µm (mean particle diameter) from Quarzwerke GmbH is used for the magnesium content in the particle mixture. This talc has a magnesium oxide content of 31%, with the remainder being bound by silicates. The particle size is determined by laser diffraction spectroscopy on an LBS Helos Quixel from Sympatec GmbH (Clausthal-Zellerfeld, Germany). The chemical composition of the particles is listed in Table . In addition, the chemical reactions with hydrochloric acid to form soluble ions are listed as examples.