Rumors of gold in the Little Belt Mountains sparked a rush of hundreds of miners into Pig-eye Basin and Yogo Gulch southwest of here in the spring of 1879. Although the placer mines soon played out, enough gold remained to hold the interest of prospectors and settlers for years. In 1895, Jake Hoover and Frank Hobson established a small placer mine on Yogo Gulch, and when they cleaned their sluice boxes, they found little gold but many small glassy pebbles, which they threw away before later discovering the stones were high-grade, gem-quality sapphires. Yogo sapphires have a distinctive deep blue cast found nowhere else in the world. Commercial mining of the gems began around 1900 and continued until about 1929, when synthetic sapphires became readily available and caused the Montana mines to close. Since then, sapphire mining has been only sporadic.