An ore seam or vein is mined by robbing ore from the side of a pilot hole using a gravity force broach to form a trench. The operators and most of the equipment, except for the broach, are located outside the trench. In weak formations the trench is filled with drilling fluid which lends mechanical support to its walls, and the drilling fluid may also be utilized in collecting the ore or mineral from the trench. Apparatus is disclosed for adjusting a parasite weight load on the broach to a desired value, and for providing a progressively advancing reciprocating drive for the broach.