AN EXPERIMENTAL APPROACH TO THE SEQUENCE OF THE STABILITY OF ROCK-FORMING MINERALS TOWARDS CHEMICAL-WEATHERING

The dissolution rates of milligrams per square metre per day for some main rock-forming minerals were measured in experiments over prolonged periods of time. Rectangularly cut pieces of single crystals or monom ineralic polycrystalline specimens were used. The experimental set-up provided for the rapid removal of all dissolved cations from the solut ion in order to maintain conditions far from chemical equilibrium. Exp eriments were performed at pH 5.5 and 4.0 at 20-degrees-C. The stabili ty towards chemical weathering decreases in the order muscovite-alkali le/pyroxene-plagioclase-nepheline-olivine-calcite. A decrease of the pH from 5.5 to 4.0 accelerates the weathering process considerably.