We have developed a confocal fluorescence microscope for observation of the dissolution kinetics at various crystal faces under varying conditions. Natural calcite (CaCO3) was chosen for the experimental samples and the dissolution kinetics was estimated from the increase in the pH value of the solution using a fluorescent pH indicator, seminaphthorhodafluors-1. Using this instrument, we investigated not only the difference in dissolution rate among various crystal faces but also the effects of the surface toughness, subsurface structure (such as lattice defects) and inhibitor on the dissolution rate. Among the (1 0 (1) over bar 4), (1 0 (1) over bar 0) and (2 1 (1) over bar 4) faces of calcite samples, the (1 0 (1) over bar 4) face dissolved most slowly and the (1 0 (1) over bar 0) face fastest. Increasing the surface area of (1 0 (1) over bar 4)-face in contact with water by scratching increased the dissolution rate. Introduction of lattice defects on the (10 14) face by He+ irradiation significantly increased the dissolution rate. Inhibition of the calcite dissolution by La3+ occurred in the order of (10 T 4) > (1 0 (1) over tilde 0) > (2 1 (3) over bar 4). (C) 2004 Elsevier B.V. All rights reserved.