"Coal."@en . "Grey's Crag Coal (Northumberland)"@en . . "330.9"^^ . . . "337.0"^^ . . . "GYCC"@en . "Coal. Stratified bedrock. Occurs onshore. Deposited during the Asbian Substage (Carboniferous Period) (337-330.9 Ma BP)."@en . "Grey's Crag Coal (Northumberland)"@en . . "stable"@en . . .