The Decline: After nearly two decades as General Manager, Randol left New Almaden in 1889. By that time, the quantity and grade of the ore were in serious decline. The ore bodies that had been so rich in the early years were gone. The amount of mercury yielded by a quantity of ore fell by drastically by the turn of the century. Worse, a new process based on cyanide chemistry offered a cheaper and more practical way to separate gold and silver from ore, making mercury increasingly redundant for the very industry it had served. Families began to leave the hilltop settlements in large numbers. A few old-timers stayed on in the company houses along the creek at the Hacienda. By 1909 Spanish Town and English Camp became ghost towns.
Bankruptcy and Closure: The Quicksilver Mining Company's Board of Directors refused to invest further in the failing mine and in 1912 they declared bankruptcy and closed the mine. The mines sat largely dormant form some time after that as a complex legal battle over the company’s massive debts left the property in a state of limbo. George Sexton, a businessman with a background in mining investments, was able to secure a lease on the property in 1915 and he began pump the water out of some of the lower levels of the mine and assess which shafts could still be profitably worked. Sexton was able to purchase the mining rights in 1917 and the vast acreage of the New Almaden district and begin the capital-intensive work of reviving the mines. He formed the New Almaden Quicksilver Mines Corporation, which became the primary vehicle for operations throughout the 1920s. He attempted to modernize the aging infrastructure and revive production, but the deep tunnels were increasingly expensive to maintain. Following George Sexton's death in 1927, that corporation too would file for bankruptcy, but the family was able to retain ownership of much of the lands.
Small-scale mining in the 20th Century: Despite the bankruptcies and decline, small scale mining continued throughout much of the 20th century, driven by independent miners who would "lease" a specific section of the hill from the owners, the Sextons and the Blacks. The days of digging deep shafts were over because they were too expensive to drain and ventilate, so they would target large open pits where ore was closer to the surface. The leasers would pay a percentage (or royalty) of the mercury they recovered back to the families, which shifted the financial risk from the owners to the individual miners, who were willing to try their luck. In the quest for increased returns, a Gould rotary furnace was installed[1] in 1939 to process ore more efficiently, which allowed the massive amounts of lower-grade ore and waste rock from the 1800s to be processed, since it still contained trace amounts of mercury. There was a brief boom in demand for mercury during World War II, which revived activity for a few more years, but activitiy finally came to an end in 1971, by which time mercury could no longer be mined profitably.