|Sapphire has been mined in southwestern Montana for more than 150 years. Operations in Yogo Gulch and Dry Cottonwood Creek have been suspended for many years. Placer deposits at the upper Missouri River and Rock Creek areas still produce gem sapphire. Gold miners first found Montana sapphire crystals in 1865 in the gravel bars along the upper Missouri River. |
| Before the 1940s, alluvial sapphire deposits were exploited mainly to supply the watch industry, but production fell sharply with the use of synthetic sapphire in watch bearings. Today, seven small-scale commercial operations are active in the Missouri River area, some of which focus on tourists. |
Due to the lack of significant sapphire-bearing host rock outcrops in the areas, the search for sapphire continues to this day.
|There are at least nine historical sapphire bars (strath terraces). All of the sapphire deposits are distributed along this approximately 14-mile section of the original river. |
Some gravel bars have a very thick sapphire-bearing layer but are expensive due to extremely thick overburden.
|Sapphire crystals from the mines at Eldorado Bar generally have different shades of pastel colors, particularly bluish green and greenish blue. Pink, purple, yellow, deep green, and the rare ruby are also found.|