Geologic Trip, The Mother Lode
Columbia State Historic Park
Placer deposits of gold were discovered at Columbia in 1850, and Columbia rapidly became one of the most famous placer mining towns along the entire Mother Lode. The central part of the town became a State Park in 1945. Many historic buildings in the town have been restored, and provide good insight into life in an 1850ís mining town. The city lies in a flat valley underlain by a bed of marble that lies within the Calaveras Complex. During the long Eocene erosion period, the marble had weathered to form a highly irregular karst surface that was pitted by numerous deep potholes and cavities. At the time of the gold rush, this irregular limestone surface was covered by about ten feet of rich gold-bearing gravel. The gold was concentrated in the potholes and cavities in the marble. The town was built on this gold-bearing gravel, and the buildings and streets of the town were continually under siege by ambitious miners. You can see the results of their efforts to get at the gold-bearing gravel at many places in and around the town, such as at the minerís cabin and the Donnell and Parsons Building site.