Yogo蓝宝石（约戈蓝宝石、优戈蓝宝石）是只有在曾经Piegan黑脚族居住的美国蒙大拿州朱迪斯盆地县的Yogo峡谷才能找到的一种刚玉。Yogo蓝宝石通常呈矢车菊蓝色，这是因为其中含有微量铁和钛。这种宝石清澈均匀，在人造光下也能保持闪耀。由于Yogo蓝宝石出现在垂直倾向的抗侵蚀性火成岩岩脉中，盈利微薄的开采只零星进行。据估计，至少有28万克拉(5.6 t或5.5 long ton或6.2 short ton)Yogo蓝宝石在地下。弗洛伦斯·哈定和贝丝·杜鲁门两位第一夫人的宝石中有Yogo蓝宝石。此外，尽管促销员声称英格兰皇冠上的宝石和戴安娜王妃的订婚戒指中有Yogo蓝宝石并不可信，但还是有很多Yogo蓝宝石在欧洲出售。如今，史密森尼学会收藏了一些Yogo蓝宝石。

Yogo sapphires are a variety of corundum found only in Yogo Gulch, part of the Little Belt Mountains in Judith Basin County, Montana, United States, on land once inhabited by the Piegan Blackfeet people. Yogos are typically cornflower blue, a result of trace amounts of iron and titanium. They have high uniform clarity and maintain their brilliance under artificial light. Because Yogo sapphires occur within a vertically dipping resistive igneous dike, mining efforts have been sporadic and rarely profitable. It is estimated that at least 28 million carats (5.6 t or 5.5 long tons or 6.2 short tons) of Yogos are still in the ground. Jewelry containing Yogos was given to First Ladies Florence Harding and Bess Truman; in addition, many gems were sold in Europe, though promoters' claims that Yogos are in the crown jewels of England or the engagement ring of Princess Diana are dubious. Today, several Yogo sapphires are part of the Smithsonian Institution's gem collection.