Montana Sapphires are enjoying renewed interest with commercial mining in full swing.
A collection of articles
The USA has significant gem resources. Here are some articles about sapphire from Montana
How Montana Gold Rushers Literally Threw Away a Fortune in Sapphires
In the mid-19th century, the cry heard across the American West was “There’s gold in them thar hills!” In the great Treasure State of Montana, little did the prospectors know that they should have instead been proclaiming the presence of one of the highest quality (and most expensive) gemstones the world over, known today as the Montana Sapphire.
In 1866, the Little Belt Mountain Range of Montana—specifically the Yogo Gulch—was awash with disappointed prospectors, tossing out the blue pebbles they found in their sluice boxes as they panned for gold. And while those pebbles were not diamonds in the rough, they were sapphires—and of an extremely lucrative variety. Other sapphires found throughout the state had been more of the industrial quality, and in hues that are less than desirable at the time: greens, pinks, or colorless.
In 1895, Montana’s reputation as a motherlode of precious sapphires was still relatively unknown, until, a gold prospector named Jake Hoover decided to send in his cigar box filled with collected blue pebbles all the way from Montana to New York City. The box landed on the desk of Dr. George F. Kunz, the most well-regarded gemologist and mineralogist at Tiffany & Co. Kunz’s meteoric rise to fame started when he began selling specimen collections of gemstones to universities across the United States as a boy, and wound up with his entrance into the Tiffany & Co. executive offices at age 23. Throughout his life, he would write, research, and accomplish much, including aiding J.P. Morgan in amassing the gems and minerals collection that would form the basis of the American Museum of Natural History’s collection. Kunz had heard of subpar sapphires from Montana before, but after examining these Yogo Gulch stones, he concluded these to be some of the best and most desirable due to their color, the formation of their hexagonal crystal shape, and their intense clarity, with minimal inclusions. These stones required no heat treatment, whereas 96 percent of the world’s sapphires do require heat treatment to achieve proper coloration.
In 1897, Kunz wrote for the American Journal of Science, and detailed the specific and ultimate coloration of sapphires from the Yogo Gulch region. He wrote that the deviation in color of the stones were “varying from light blue to quite dark blue, including some of the true ‘cornflower’ blue tint so much prized in the sapphires of the Ceylon… Some of them are ‘peacock blue’ and some dichroic, showing a deeper tint in one direction than in another; and some of the ‘cornflower’ gems are equal to any of the Ceylonese, which they strongly resemble,—more than they do those of the Cashmere.”
Previously, sapphires of this shade and depth of color only came from the Kashmir region in India, and thus today at auction one often hears about the highest-selling sapphires as Kashmir sapphires, in the same way some of the best diamonds are known as Golconda Diamonds, a region which denotes their top quality. Yogo Gulch sapphires are the ideal blend of aluminium, oxygen, and titanium, with the presence of titanium integral to creating the perfect blue hue.
So, how does color and quality translate into dollar signs? Today, some more common Montana sapphires can fetch $1000—$4000 a carat, but the pure and bright “cornflower” blue stones from Yogo Gulch often hit the benchmark of $10,000—$14,000 a carat.

Yogold USA
From an article by Brecken Branstrator@nationaljeweler.com Click here to read the full article
Yogo Gulch, Montana—The Yogo Mine in Montana is producing again, thanks to Yogold USA.
The mine, which produces the popular Yogo sapphires, was dormant for nearly four decades.
A few years ago, Yogold USA entered the arena. The mining company first entered into an exploration agreement, which ended December 31, 2022, and then it transitioned into a lease with an option to purchase.
Its lease and option consist of 1,563 acres of deeded ground, where the company is simultaneously engaged in commercial production and underground development as well as surface exploration, President Jerod Edington confirmed to National Jeweler.
There are two historic workings in the mine.
A British group conducted surface mining on top and eventually sunk a shaft to 250 feet underground.