Dwarves of the Grey Mountains
The Dwarves of the Grey Mountains were the Dwarves of Durin's folk who lived in the Grey Mountains in northern Middle-earth. They started to gather in the Grey Mountains in Third Age 1981 after a Balrog was awoken in their ancestral home of Khazad-dûm. Another portion of their House lead by King Thráin I established the Kingdom Under the Mountain at Erebor. Some years after leaving Moria Scatha the Great Worm of the Ered Mithrin began to afflict the Dwarves, and all who lived in that region. Until Fram of the Éothéod slew him. Bringing peace from the Long-Worms from many years till the Wars of the Dwarves and Dragons. But their was a feud between the Dwarves and Fram, for he refused to yield any of the treasure of Scatha to the Dwarves. Instead he sent a necklace of Scatha's teeth to them, saying "treasures like these are hard to come by". for this insult it is said the Dwarves slew him.
In 2210 King Thorin I, learning that most of his people were gathering in the Grey Mountains, left the Lonely Mountain to join the Dwarves to the north. for those mountains were rich and little explored. For 360 years Durin's folk prospered in the Ered Mithrin, but the Dragons in the wastes beyond began to multiply again and made war on the Dwarves in 2550, and plundered their works. After 19 years the Wars of the Dwarves and Dragons came to an end when a great Cold-Drakes | Cold-drake]] killed King Dáin I, and his second son Frór at the door of his hall. A year later most of Durin's folk abandoned the Grey Mountains. Grór, youngest son of the king went with many followers to the Iron Hills. While the new King Thrór along with his uncle Borin, and the remainder of the people went back to Erebor.
Their still was a remnant of the Dwarves in the Ered Mithrin after the core of the population left, they were probably few. Working whatever mines they could hold from the Orcs and Dragons. So it is likely that the Dwarves reclaimed all their old halls and mines sometime during the Fourth Age.