|View from Prospector's Gap into Mitchell Canyon toward Clayton (Mount Diablo State Park, California)|
An interpretive board at Prospector's Gap informs about what prospectors once had in mind before the ridges and canyons became recreational open space: Mining at Mount Diablo. Mercury (quicksilver), copper, coal and travertine (a form of limestone) were mined around the mountain peaks. Traces of gold and silver were found, but not enough to also find investment. A few quarries still provide rock for construction work.
According to the board, during World War II, when the demand for mercury increased, the Diablo quicksilver district became the 9th most productive U.S. source of the slippery metal. The mining activities left their traces:
While mercury mining on Mt. Diablo stopped by 1952, residues remained—mercury, lead and arsenic used to extract the [other] metals [such as gold elsewhere]. The hazardous byproducts still leach from the mines or from mine “tailings,” piles of broken rock or gravel left behind. The materials break down, ecpecially in the rain, and contaminate some park streams and near reservoirs.
And the winter of 2016/2017 saw a lot of rain, which also broke down sections of park roads and caused wash-outs along hiking and biking trails.
Keywords: Mount Diablo, mining history, mine tailings, quicksilver, environmental pollution.
|Cones of gray pines at Prospector's Gap in Mount Diablo State Park|