The chalybeate springs in
Hampstead in north London were part of the reason why the suburb became
fashionable in the eighteenth century. People would go up their to "take the waters" for their health. They are very rich in
minerals, so I suppose to an impoverished
diet they could indeed be a valuable source of
health.
There's still a couple of sources available for public drinking in Hampstead. One is a tap over a trough in Well Walk, donated many many years ago. This has recently been restored and is again drinkable.
The other one is a basin on a grassy hillside above Kenwood, the stately home, on Hampstead Heath. Here the tangy, sharp water bubbles up and you can drink it by cupping your hands.
All around the area the water (which feeds into the River Fleet among others) is accompanied by a bright orange metallic sediment, which looks startling, but is I think just the deposit of the mineral springs.
In Pickwick Papers, which begins with a search for sticklebacks in the ponds on Hampstead Heath, they talk about the chalybeate springs. (I can't remember whether they're the same ones or somewhere different.) Sam Weller says, "I thought they'd a wery strong flavour o' warm flat-irons." And someone (not Mr Pickwick) replies, "That is the killibeate."