sentences:  Silver veins were first discovered in the Montezuma district of Summit County in 1864.Despite the early silver discoveries, Colorado's largest silver district, Leadville, was not discovered until 1874.The largest current source of silver in Colorado is as a byproduct of gold mining at the Cripple Creek & Victor mine, a large open-pit heap leach operation owned by AngloGold Ashanti at Victor, Colorado.