Montana Sapphires

Montana sapphires refer to all sapphires which are mined from the state of Montana, in the east of the United States. Montana has a rich heritage when it comes to the mining of precious metals, notably gold, silver and valuable minerals; and in later times gemstones. Owing to the relative abundance of these wealth-generating resources, Montana has come to be known as The Treasure State, with its state motto ‘oro y plata’ which reads as gold and silver. Our discussion here is of a very specific treasure that comes from this US state: sapphires. In what parts of Montana are these sapphires found, what makes them different from sapphires from the rest of the world, and the specific variants in the Montana family of sapphires. Today the popularity of Montana sapphires is strong, that it has now come to be associated with sapphires from the United States, and considering the particular appeal of the Yogo variety of Montana sapphires it has come to be known for possessing a certain distinct appeal in the world of corundum gemstones.

What are Montana Sapphires?

Montana sapphires are like any other natural sapphires in that they are conundrum based gemstones, that get their colour from the presence of trace elemental impurities that enter their structure in the course of their development deep underground. The main factor that sets Montana sapphires apart, one that is associated with their regional description that precedes the term, is that they are arguably the most popular type of sapphires stones that are minded outside of Asia and Africa. In addition to having the distinction of being among the more recognized sapphires in the world, sapphires mined in this region do come with a certain set of characteristics, that sets them apart from the rest.

Montana Sapphire Mining

Montana sapphires are sourced from two types of deposits. The popular secondary deposit, which is alluvial and the rarer primary deposits, for which sapphires from this region have built up a reputation. The main secondary sapphire deposits in this region come from the Missouri River and Rock Creek, Two major rivers, with the Missouri River being the largest in North America. Since corundum stones tend to wash away over time, due to geological activity from their primary sources, the areas surrounding these rivers become deposits for these gemstones. Montana sapphires mined from secondary sources come in a wider variety of colours and are also heated to improve their natural colour. Any study of sapphires from this part of the world must involve a discussion of a certain sub-variety of sapphires from this region known as Yogo sapphires: corundum gemstones from the state of Montana that mined from a specific region known as the Yogo Gulch. The mining for Montana sapphires began as a secondary concern to the main gold mining rush that was all the rage during this time. This meant that the technical know-how and the industry capacity had to be built up to mine this resource, which combined with questions over the viability of the mines required considerable investment to get the projects off the ground, such as heavy machines to remove the gravel, under which lay the gemstones in the secondary deposits.

Yogo Sapphire Mining

Yogo sapphires are a subgroup of Montana sapphires and are arguably the most recognized variety, These gemstones are mined from an area that forms part of the Little Mountain Belt in Judith county, and are known for their cornflower blue colour: which is one of the most sought after blue hues in the range of coloured sapphire stones. The origins of Yogo sapphires mining goes back to the time following the gold rush in the United States. During the later stages of the 19th century, a man named Jake Hoover discovered distinct blue stones in the Yogo Gulch, which seemed alien at the time, in this part of the world. And the mining company he set up to find gold send these stones for gemological study, which were then revealed to be sapphires. Subsequent discoveries revealed a vast natural reserve of corundum gemstones, the largest in the United States. Today Montana sapphires are among the top sources of natural sapphire in the world, in the time since its discovery sapphires from Yogo Gulch have produced millions of carats.

Characteristics of Yogo Sapphires

Yogo sapphires are known for their natural rich colour, and high clarity and that most stones do not require heat treatment. A distinct feature of Yogo sapphires is the manner in which there are sourced. Since most sapphires that are mined in the world are taken from secondary sources, usually alluvial deposits near water-rich regions. Yogo sapphires on the other hand are sourced from primary sapphire mines: as the stones are taken directly from the volcanic rock, that has been carried to the surface from the Yogo Dike. What makes the Yogo variety of Montana sapphires different is that tend to be larger, with sapphire stones over 1.00 carat, not an uncommon find, along with their lower iron content which gives them their distinct cornflower blue. With certain estimates putting the number of cornflower blue sapphires stones from this region as high as 90 per cent.

As noted Yogo sapphires tend not to be heat-treated, and further study under microscopic technologies reveal sharp edges to the stone that are not found in gems sourced from secondary deposits in the region. In addition to their higher level of natural clarity. Another key feature that sets the Yogo sapphire apart from other sapphires from Montana is that they have a lower number of rutile needles: which are silk-like inclusions that reduce the gemstone’s value. Another interesting feature of Yogo sapphires is that certain gemstones from this region contain garnets: extremely small, microscopic garnet within them. This is a result of the character of the rock where sapphires are sourced with pyrope, almandine, grossular garnets being the most popular. Another interesting feature of Montana sapphire is colour banding: which is lower in Montana Sapphires, especially the blue variety. Unlike sapphires from other parts of the world (Ceylon), where colours are unevenly spread across the gemstone. Here is a quick breakdown of Yogo Montana sapphires:

Regular Montana Sapphires vs Yogo (Montana) Sapphires

As noted Montana sapphires which are not mined from Yogo Gulch primary deposits are different from the more popular variety. Montana sapphire mined from secondary sources tends to come in a variety of colours, which tend to be lighter in their saturation. Such Montana sapphires are known as having pastel colours, which are appealing in their own right. Sort of like Australian sapphires. However, these stones tend to be heated to increase their saturation. So contrary to what people may think Montana Sapphires (i.e. sapphires from the US) are often treated. That is if you are not getting them from Yogo Gluc deposits, which puts them into the special category of the Yogo variant of the Montana sapphires.

Montana Sapphire Engagement Rings

When it comes to sapphires, and gemstones in general a key feature of their quality and value is their use in the world of fine jewellery. Sapphires are among the top choice when it comes to the making of fine jewellery like engagement rings, and Montana sapphires over the years have risen in status to meet the demands of the modern consumer: considered to be among the finest sapphires in the world. Whilst they lack a variety of colours that match the rich saturation of those sapphires from Asia, Montana sapphires do rise up in other areas like clarity, which is a key factor in determining gemstone quality in engagement rings. And when it comes to quality blue sapphires, the Yogo variant is a solid choice, with its rich Cornflower blue colour and its status as a predominately untreated stone. So for the adventurous buyer, who wishes to buy American, the Montana sapphire engagement ring might be the way to go.