The Dwarf Mines (ドワーフ鉱山, Dowāfu Kouzan) is a location mentioned in the original Suikoden.
Sanchez mentioned that the Toran Liberation Army paid a lot of money in order to obtain the blueprint for the Fire Spear from the Dwarf Mines[1]. As dwarven treasures, including blueprints and plans for weapons are normally kept in the Dwarves' Vault, it is likely these two locations are one and the same or at least very deeply connected.
The term is also in use in the original Japanese script[2].