The Denver Mineral & Gems Showcase is the second-largest gathering of gem and mineral shows in the U.S. after Tucson. The fall session features 13–14 shows spread across five main venues and lasts about a dozen days : The largest and most iconic venue is the Coliseum, which hosts three of the shows at the National Western Complex. Coliseum show + National Western Complex (Denver Expo Gem Show, Denver Mineral Show, Miner's Co-op Mineral Show) : Denver Mart at the Denver Minera