In 1871, John W. Mackay, James G. Fair, James C. Flood and William S. O'Brien, organized the Consolidated Virginia Silver Mine near Virginia City, Nevada, from a number of smaller claims on the Comstock Lode. Later they added the near-by California mine. For three years after large ore bodies were uncovered in 1874 the two mines produced $3,000,000 per month. In 1876, for exhibition purposes, $6,000,000 was taken in one month from both mines. Production began to fall off in 1879 but in twenty-two years of operation the two mines yielded $150,000,000 in silver and gold, and paid $78,148,800 in dividends. Bonanza is a Spanish term, meaning a rich ore body; the large vertical ore body they discovered in the hanging wall of the Comstock lode became known as the big bonanza.
References
Dictionary of American HistoryJames Truslow Adams, New York: Charles Scribner's Sons, 1940