SPELEOTHEMS FROM AN ABANDONED GOLD MINE, SAN BERNARDINO MOUNTAINS, CALIFORNIA

An abandoned gold mine, located in Las Flores Canyon, 15 miles northeast of Los Angeles in the San Bernardino Mountains contains a variety of speleothems. The mine consists of a main horizontal shaft, approximately 200 m long, and a secondary horizontal shaft, approximately 75 m long. The mine follows a contact between the Pelona Schist and Cretaceous granitoids and was abandoned approximately 100 years ago. Groundwater flow through the mine has led to the precipitation of a variety of features, including flowstone which covers much of the walls of the mine, small stalactites and soda straws along the roof of the mine, and cave pearls along the mine floor. The mine exhibits a patchy distribution of flowstone; some areas of the mine roof and sides are completely coated while other areas exhibit very little coating; however, flowstone coatings typically get thicker in the deeper parts of the mine. Stalactites are typically small, on the order of a few millimeters, soda straws are typically longer, up to 2 cm in length. The cave pearls range from a few millimeters to 2 cm in diameter. Many of the cave pearls have been cemented together to form grapestone, and in places a flowstone crust up to 5 mm-thick covers the floor of the mine. The cave pearls are typically comprised of layers of calcite crystals growing perpendicular to a central nucleus; layering of the cave pearls may be the result of alternating wet and dry seasons. The source of the calcite is most likely from marble contained within the Pelona Schist.