Shorty pans for gold – sketch by the author. California’s rich gold mining heritage should not end with ‘historical’ mining: But the naivety of the public and green movements, over-regulation by bureaucracies, costs and liabilities of mining, and exploration costs have left the state broke.
In addition to gold, the state yielded by-product platinum, sapphire and benitoite from its serpentinite belt in the Sierra Nevada.
Alpha and Omega historical hydraulic gold mines, California This belt, known as the Mother Lode, was outlined by gold discoveries in quartz veins in a region about 4 miles wide and miles long that reached north from the Sixteen-to-One mine at Alleghany to Mormon Bar in the south. The precious metal was found in quartz veins in phyllite, schist, slate and greenstone. The more productive veins were discovered along at contacts between two different rock types.
Where extensive erosion occurred, major placers formed downstream in Holocene and Tertiary gravels. Broad zones of mineralization found in weathered lodes that were hydraulically mined. The Mother Lode was legendary for its incredibly rich pockets of gold. The richest contained crystalline gold within the Alleghany-Downieville region 75 miles northeast of Sacramento.
In the s, a pocket intersected at the Sixteen-to-One yielded nearly 95, ounces of gold! But those of the Allegany district were especially rich Clark, Some pockets showed enrichment of iron, others did not.
Many of the rich pockets were small but found at or adjacent to serpentinite-slate contacts. In some, quartz-mariposite a green mica was found. Near serpentinites, many of the quartz veins split or were bent. Such structures produced gold pockets in some cases. Other high grade pockets were found at vein intersections or in shears.
Most were mined by hydraulic methods because of the broad zones of gold mineralization with numerous crisscrossing quartz veinlets. Not only did the veinlets contain precious metal, locally some fractures contained gold.