Recent microfluidic experiments  have allowed for direct visual observation of the instabilities that can occur during fracture dissolution. Deionized water is injected at constant flow rate over a thin (0.5mm) chip of gypsum (38mm x 33mm), replacing the initially saturated solution. Dissolution of gypsum occurs mostly near the fresh water inlet, where the solution is least saturated. After about 48 hours the gypsum near the inlet has dissolved fully, as can be seen from the empty region near the inlet in the left panel of Figure 1. The irregular dissolution front indicates an instability , which is driven by a coupling between fluid flow and dissolution. Small perturbations in surface of the gypsum (of the order of 5-10 micron) generate fluctuations in the flow field and enhanced dissolution in regions where the flow is larger. This feedback mechanism causes an exponential growth of sinusoidal perturbations, of which a single mode is preferred because it has the highest growth rate . The predicted wavelength agrees well with the early stages of dissolution of the gypsum chip .
Numerical simulations  have been used to model gypsum dissolution within the same microfluidic geometry. The fingering pattern is similar to the experimental observations (Figure 1). In particular we note the typical competition between the growing fingers that leads to patterns of hierarchical growth . A further point of contact is in the development of the partially dissolved region ahead of the tip of the fully dissolved finger. This can be seen most easily in the profilometry image (Figure 1, right panel), but it is also visible in the simulation (Figure 2).