Analcime of hydrothermal origin occurs in the gabbros and in the amphibolites and granulites. Crystals from the different rock suites display the same unusual characteristics upon dissolution: the interior is much more susceptible to attack than the outer growth zone; the former may be converted to a skeletal boxwork, and the latter may suffer extreme differential dissolution along successive narrow growth horizons. Pseudomorphs of adularia after analcime have been found in various stages of development, from partial to complete replacement. Some of the latter preserve the very delicate dissolution structures in detail. Up to fourteen growth horizons have been detected in the outer millimetre of the crystal. This demonstrates that both the growth and dissolution of analcime occurred prior to the formation of adularia, an event that has been dated.