Friday, February 21, 2014

Yogo Sapphires: Montana's Rare Treasures

This necklace and its matching bracelet feature 108 rare Yogo Gulch Montana sapphires. Photo © 2014 EraGem Jewelry.

This necklace and its matching bracelet feature 108 bezel-set Yogo Gulch Montana sapphires. Photo © 2014 EraGem Jewelry.

by Angela Magnotti Andrews

 Rare and beautiful, Montana's Yogo sapphires are among the world's most valuable sapphires. Deep cornflower blue with even color and rich saturation, these beautiful gemstones are found in only one location in the world, Yogo Gulch, located in the Judith River basin in north central Montana.

 Although these blue beauties were first discovered by gold miners in 1878, in the silt deposits along Yogo Creek, these miners had only one thing on their list to collect, and it wasn't blue {4}. Tossed aside, these pebbles continued to collect on the sand bars of the small river, largely unnoticed until the 1890s.

 In about 1894, Jake Hoover, a well-known Montana frontiersman and adventurer, staked a claim along Yogo Creek to hunt for gold. He and his partners, Simon Hobson and Jim Bouvet, spent $40,000 to begin a bona fide gold mining outfit in the region {1}. It took them one year to collect 40 ounces of gold, which when split three ways netted each of them $233. Things were not off to a good start for the trio.

 However, by a stroke of genius, one of the men filled a cigar box with the tiny blue pebbles which appeared more common than gold in the alluvial deposits. What may have started as pure fascination turned into profits swiftly after this man sent his box of rocks to an assayer. Most accounts credit Jake Hoover with the collection; however, this is in dispute, as you will soon see.

 The assayer sent the box of stones to New York, where Tiffany & Co.'s gemstone expert, George Frederick Kunz, examined them. In an article written in 1897 for The American Journal of Science, Mr. Kunz credits the discovery of these stones to Mr. Hoover's partner, Simon Hobson, writing, "Mr. S. S. Hobson, of Great Falls, Montana, the original discoverer of the gems at Yogo Gulch, states that at that point there are two veins (dikes?) containing sapphires, which have been traced for a distance of seventy-five hundred to eight thousand feet in an east-and-west course..." {Kunz, p. 418}.

 Going on, Mr. Kunz highlights the distinction between Yogo sapphires and other Montana Sapphires, calling specific attention to the unique shape of the crystals (rhombohedron x), as well as striations unique to this particular variety. These discoveries were of import because the same geological conditions appeared to have produced very distinctive results in different parts of the state. This was of great geological interest at the time. Mr. Kunz noted that the sapphires found in Yogo Gulch showed the greatest promise for being of worth to the gemstone industry. While Montana sapphires are found in a variety of colors, it was these cornflower blue stones, reminiscent of the highly sought-after Ceylon sapphires, which stood the greatest chance of capturing a share of the gemstone market. Whether before or after this article came out, Tiffany & Co., under the advisement of Mr. Kunz, sent a check to the Montana miners, motivating them to abandon their efforts to find gold and set their sights on discovering the mother lode for what Mr. Kunz deemed "the finest precious gemstones ever found in the United States" {1}.

 In 1900, Tiffany & Co. exhibited two remarkable brooches at the Exposition Universelle in Paris, France. Both featured American freshwater pearls and Montana sapphires from the Yogo Gulch. An accompanying brochure published by Tiffany & Co. reported that George Kunz deserved full credit for bringing Yogo sapphires center stage {3}. Tiffany & Co.'s manufacturing ledger, dated November 29, 1899, listed $2,500 as the retail price for one of these brooches and a price tag of $900 for the other one {3}.

It is clear why the jewelry firm paid such a hefty price for the stones. With returns like that, Tiffany & Co. stood to make a pretty penny on these matchless Montana sapphires. Yogo sapphires remain among the most precious blue sapphires on the market. Their true-blue color is only part of their appeal. Yogo rough is generally small and flat, rendering cut stones greater than 0.5 carats of premium value to collectors and jewelers.

Also, although there are large veins of Yogo sapphire rough beneath the dikes, mining for the unique sapphires presents numerous difficulties. Currently, no one is actively mining for the stones. Truly, this stunning necklace and bracelet set, featuring 108 dark violet-blue Yogo sapphires, is as rare and beautiful a find as a large Yogo sapphire would be today.


  1. Gem Gallery, The. "About Sapphires of Montana." Accessed February 21, 2014.
  2. Kunz, G. F. "Sapphires from Montana," The American Journal of Science, 1897, pp. 417-420.
  3. Phillips, Clare. Bejewelled by Tiffany, 1837-1987. New Haven, CT: Yale University Press, 2006.
  4. Wikipedia. "Yogo Sapphire." Accessed February 21, 2014.

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