a metal-rich moon (Which looked exactly the same as an icy moon does on the System map, by the way...
Oh, that's interesting. Do you recall what sort of planet (Class V Gas Giant?) it was a moon of, what the local star was and what distance the planet was from the star?
The ordinary metal-rich worlds (as distinct from high-metal-content) seem to form almost exclusively as the closest worlds to the star, though I have seen rare occasions where there's an HMC world immediately before a MRW.