While Black Chasm Cavern was likely known about by the local Miwok people who existed in this area long before the gold rush, the first documented exploration occurred in 1854 when a group of explorers braved the unknown to discover the phenomenal beauty that exists below the surface including a bright blue lake and millions of sparkling crystals that seemed to twist from the cavern walls in every direction, we now know these unusual formations as ‘helictites.  Simple tours were held at Black Chasm in those early days, barely penetrating the cavern system that we know today.  Shortly afterwards, with the decline of the gold rush, Black Chasm was abandoned and largely forgotten about except for by a handful of speleologists that continued to explore the chasm and discover the seemingly endless beauty of  the cavern.  Over 100 years after its discovery Black Chasm was recognized by the federal government for the abundance of the unusual and rare speleothems called “helictites” that grow throughout the cavern and declared a National Natural Landmark in 1976.  Twenty years later Black Chasm began to be developed as a show cave with the construction of environmentally friendly   steps and walkways Today guests can explore the cavern via these platforms  and view the dazzling array of crystals throughout the cave guided by an experienced and knowledgeable cavern naturalist.