Existing comment:
The California Stamp:
Soon after miners discovered gold in underground quartz veins, mills were brought in to process ore. Dating back to at least the 1500s, the mills used heavy iron pounders called stamps to crush the rock.
Each mill had a series of stamps equipped with iron "shoes." Partially broken quartz was fed into bins behind the stamps and then into mortars holding dies on which the shoes fell. Each stamp rose and dropped separately.
California quartz miners improved stamp mills by changing from soft iron to cast-iron shoes, dies, and mortars. They also introduced stamps that rotated on their vertical axis with each rise and fall. The result was the "California stamp," a machine so efficient it was used in gold mining throughout the world. |