Dwarves of the Blue Mountains
After the War of Wrath, much of the Ered Luin fell into the sea, taking the Dwarf city of Nogrod home of the Firebeard Dwarves with it (it then became the Gulf of Lune), and ruining Belegost to the north, the home of Broadbeams. Many of these two Houses left the Ered Luin for Khazad-dûm home of the Longbeards, brining much lore and craft and swelling its numbers. While some stayed to help rebuild their homes.
For hundreds of years the remnants of the Firebeards and Broadbeams toiled in the Blue Mountains. Working the mines and buiding new realms.
They most likely traded with Elves of Mithlond during the Second through Fourth Ages, with the Men of Arnor in the late Second Age through the Third Age, and with Durin's folk throughout the two Houses histories.
When the Balrog drove the Dwarves out of Khazad-dûm in 1981, it is speculated that the Firebeards and Broadbeams went back to the Ered Luin and reestablished their kingdoms. And had a lesser amount to do with the Longbeards except through trade. Until the murder of their King Thrór. Who was killed by Azog the Chieftain of the Orcs of the Misty Mountains. The King's son Thráin sent messangers to all the Houses of the Dwarves requesting aid. They all sent troops and helped fight in the War of the Dwarves and Orcs.
The Dwarves of the Blue Mountains, lived in their halls through the Fourth Age, but nothng is known about what happened to them.