Mt. Mica Mine, Paris, Maine-Maine Mineral AdventuresMt. Mica is the oldest gem mine in the United States and one of the few still in operation in Maine. Mt. Mica is presently owned and operated by Gary Freeman.mica mining in mountain,mica mining in mountain,Digging deep into Western North Carolina's mining history - Smoky .Jun 1, 2013 . Because of the region's mountains (some of the oldest in the world), North Carolina is the nation's leading producer of mica, that glass-like.