About Sapphires of Montana

Montana is known as the Treasure State because it is rich in many mineral and gemstone sources, including two types of sapphires: the Yogo Sapphire from the central area of the state, and Fancy Montana Sapphires found mostly in the western half of the state.

Montana Sapphires — Gemology

A Rainbow of Colors

Montana Sapphire
Montana Sapphire
Fancy Montana Sapphires are found in three major areas in the western half of the state: Missouri River near Helena, Rock Creek in the Sapphire Mountains, and Dry Cottonwood near Deer Lodge. These sapphires vary greatly from the Yogo Sapphire in that most of the sapphires require heat treating. They are also found in secondary mines, meaning they are found not in their original rock matrix veins but have been forced up closer to the surface which makes them much more accessible than Yogo sapphires. We are lucky, here in Montana, as we have more variety of colors in sapphire than any other locality in the world.

Fancy Montana Sapphires are found in three major areas
Fancy Montana Sapphires are found in three major areas
Missouri River area yields sapphires of the largest size for Montana. Cut stones from this location may weigh up to ten carats, but are rare. Some gems over twenty carats have been found but are exceptionally rare. These gems are found in a more light steely-blue color to a blue/green color. Heat-treating* of these stones removes undesirable cloudiness (silk) from the gem and can improve their color.

Montana Sapphires come in a rainbow of colors.
Montana Sapphires come in a rainbow of colors.
Rock Creek sapphires are found in abundance and come in a multitude of colors. Smaller in size than Missouri River sapphires, these more rounded sapphires are found in an assortment of colors: greens, light blues, pinks, yellows, and oranges. These stones respond very well to heat-treating, producing an amazing array of intense colors. Some of the stones transform into intense blue colors. It is very easy to distinguish these heat-treated stones from natural Yogo Sapphires. Sizes for Rock Creek sapphires are generally one carat and less. Stones of three to five carats are rare but occasionally found.

Dry Cottonwood sapphires are very similar in nature to the sapphires from Rock Creek. This site is a much smaller deposit than Rock Creek.

*Heat-treating is the process of heating sapphires to near the melting point to improve color and/or clarity. The vast majority of sapphires and rubies worldwide are enhanced this way. It is a permanent process of changing the stone. Standard heat-treating is generally accepted in the gem industry for the processing of sapphires. The Gem Gallery supports full disclosure of any treating process used on any gemstone. Our natural Yogo Sapphires and untreated fancy colored Montana Sapphires are separated and identified for exactly what they are. The Gem Gallery can offer you the best of these stones, totally natural Yogo Sapphires and treated and untreated fancy colored Montana Sapphires. Both are treasures from Montana, the Treasure State.

Heat-treated, cut Montana Sapphires
Heat-treated, cut Montana Sapphires
Rough Montana Sapphires, uncut
Rough Montana Sapphires, uncut


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