Ralph Compton Lost Banshee Mine (The Sundown Riders Series)

Two miners have worked their claim for a year and are barely eking out a living. One night, one of them gets drunk and buys a treasure map from a shady character who says that it came from an infamous bank robber. The other miner thinks the map is a complete fraud, but then details start clicking into place. Maybe they have the key to their fortunes after all! But word gets around, and the infamous bank robber shows up looking for his map. They will have to fight off hostile Indians, miners, and a dangerous felon to get the cache of gold.