While Monnette was trained as an attorney, his father's foray into mining in 1904-1906 changed his career path. In 1906, the elder Monnette struck a significant gold vein in the previously thought tapped out Mohawk Mine, Tonopah, Nevada (near Goldfield, Nevada). The strike, known as the Monnette-Hayes Lease, with mining expert G. H. Hayes and set records for the value of the ore shipped in 1906. Eventually, Mervin Monnette realized a $5,000,000 profit on the Mohawk, which he assigned to his son for investment.