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For Stokes waves in finite depth within the neighbourhood of the Benjamin–Feir stability transition, there are two families of periodic waves, one modulationally unstable and the other stable. In this paper we show that these two families can be joined by a heteroclinic connection, which manifests in the fluid as a travelling front. By shifting the analysis to the setting of Whitham modulation theory, this front is in wavenumber and frequency space. An implication of this jump is that a permanent frequency downshift of the Stokes wave can occur in the absence of viscous effects. This argument, which is built on a sequence of asymptotic expansions of the phase dynamics, is confirmed via energetic arguments, with additional corroboration obtained by numerical simulations of a reduced model based on the Benney–Roskes equation.
Comparison of the infrared spectra of georgeite and a phase which can be reproducibily synthesised in the laboratory shows that the mineral is an amorphous analogue of malachite, Cu2CO3(OH)2. Synthetic studies also explain the chemical conditions under which georgeite may form, as well as those which can cause it to react to either malachite or chalconatronite. Parallels may be drawn between the laboratory observations and known mineral associations of georgeite.