Saturday, 2 February 2019

Montana Sapphire

Sapphire has been mined in Montana for more than 150 years. Gem quality sapphires have been mined in four main areas in southwestern Montana. 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 discovered 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, some of which focus on tourists. Due to the lack of sapphire-bearing host rock outcrops in the area, the search for sapphire continues to this day.
The Missouri River flows from southeast to northwest. In addition to other occurrences, there are at least nine historical sapphire bars (strath terraces). All of the sapphire deposits are distributed along this 14-mile section of the original river.

Some gravel bars have a very thick sapphire-bearing layer but are expensive to mine due to 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.
See ----->Yogo Gulch Sapphire