The Sapphire Mountains are a mountain range in the state of Montana, running from the city of Missoula southwards for about fifty miles. The ridge runs parallel to the much larger Bitteroot Mountains, and forms the western edge of the Bitterroot Valley. The distance between the two ranges is fairly small, somewhere between five and twenty miles, depending on location.

Although they are close together, the Bitteroots and Sapphires are very different mountain ranges. The Sapphires are made of Precambrian rock that was already well-weathered and eroded when the Bitterroots appeared, in Cretaceous time. The Bitterroots were actually a granite intrusion that appeared directly underneath the Sapphires, sending them sliding downwards and to the east. In the intervening dozens of millions of years, the area between them has filled in with rocks and gravel eroded from both ranges, forming the Bitterroot Valley.

Their separate and older origin has made the Sapphires a different range from the Bitterroots. They are eroded and rounded, having the topology of high hills more than mountains. Their peaks are between six and eight thousand feet above sea level, (or between three and five thousand feet above the floor of the Bitterroot Valley), which makes them too low to get much snow pack or to create their own weather due to adiabatic cooling. Because of this, they generally have much less vegetation than the Bitterroot range, having an open steppe biome, interspersed with some denser pine forests. Their smaller height also means that they were not glaciated during the ice ages, and therefore do not have the dramatic glacial topology of the Bitterroots.

Despite their relatively smaller heights, they are still fairly rugged mountains, and there are only two roads across them: one of them a forest service road, and the other a gravel highway that is only open from May until September. Compared to other areas of Montana, they are not considered a great draw for outdoor activities, but there are still quite a few forest service roads into them for the determined hiker or camper.

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