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。
^在现代黑脚族语言的字典中,没有任何接近“yogo”的词的意思和促销员的那些受欢迎的推测的意思相近。黑脚族表示求爱这样的概念时的单词是isawaanopaat,表示蓝色的单词是ótssko,表示天空的单词是sspóóhtsi(Frantz & Russell 2000,第304, 286, and 402頁)。
^Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. Corundum. Handbook of Mineralogy(PDF)3. Chantilly, VA: Mineralogical Society of America. [December 5, 2011]. ISBN 978-0-9622097-2-7. (原始内容存档(PDF)于2012-06-14). 注:蓝宝石是多种不同颜色的刚玉
^Field Guide, Little Belt Mountains. Science Education Resource Center, Carleton University. [October 29, 2011]. (原始内容存档于2022-12-07). Note: Click map.
^ 5.05.15.2
Weed, Walter Harvey; Pirsson, Louise Valentine. Geography of the Little Belt Mountains, Montana. Washington, DC: United States Geological Survey, Government Printing Office. 1900: 317–331, 396–400, 447–459, 471, 476, 486, 494, 502–504, 556, 568, 576 [October 29, 2011].
^ 18.018.1
Kane, Robert E. The Sapphires of Montana – A Rainbow of Colors. Gem Market News. January 2004 (Glenview, IL: Gem World International). January–February 2003, 22 (1): 1–8.
Voynick, Stephen M. Yogo: The Great American Sapphire March 1995 printing, 1987. Missoula, MT: Mountain Press Publishing. 1985. ISBN 978-0-87842-217-3.
Frantz, Donald G.; Russell, Norma Jean. Blackfoot Dictionary of Stems, Roots, and Affixes 2nd. Toronto, ON: University of Toronto Press. 2000 [1995]. ISBN 978-0-8020-7136-1.