Modern Marvels (1993) : 3x6

It was called the "mother lode", a deposit of silver so massive that it would produce $300-million in its first 25 years of operation, establish Nevada as a state, and bankroll the Union Army in the Civil War. Named after an early investor, we'll see how the Comstock Lode, discovered near Virginia City, proved to be a scientific laboratory from which vast improvements in mining technology and safety were pioneered, including innovations in drilling, ventilation, drainage, and ore processing.