"Stone Lodge was situated on a moor within a mile or two of a great town — called Coketown in the present faithful guide-book."

I wonder what "coke" meant to Dickens.When I was young, very large quantities of soft coal were converted into gas for home heat, and the residue, a gray sponge was called coke, which was used in making good steel, because the sulfur had been removed.It was also used for home heating.
The sponge was composed of coal similar to anthracite,hard coal. Dickens can have known none of this. Remember that the Titanic sank because its steel plates were brittle from the impurities in the coal used in smelting it.