What are Montana Sapphires and Yogo Sapphires?

A Montana sapphire is, simply, a sapphire from Montana. Yogo sapphires are also Montana sapphires, but originate from a particular deposit known for its excellent cornflower blue color.

Both sapphires and rubies are gem-quality corundum. Rubies are the red variety, while all other colors are sapphires.

With a hardness of 9 on the Mohs scale, only diamond can scratch a sapphire. Furthermore, sapphire doesn’t fracture easily, making it one of the best jewelry stones.

In terms of gem production in the United States, sapphire is commercially mined only in Montana. Fee digging sites in North Carolina also produce some sapphire, but only a small amount of sapphire occurs in North Carolina.

History and Geology of Montana Sapphires

Four areas of Montana produce gem-quality sapphire. In 1865, gold rush prospectors discovered sapphire in the gravels of the Missouri River. At the time, these stones were waste that got in the way of extracting gold because no facilities for faceting and polishing sapphire existed anywhere nearby. As a result, these pebbles were nearly worthless. Nowadays, these deposits produce the largest of Montana sapphires, with 20-carat specimens not unheard of.

Prospectors discovered sapphire…