Chasing the Blues: A Comprehensive Guide to Blue Slag (What Is It and Where To Find It)

All About Blue Slag

Blue slag is a man-made rock created as a by-product of iron smelting. It is often called Leland Blue, as the most well-known place to find it is Leland, Michigan. It can also be found in Tennessee and Sweden, though these sites are not as well known and do not produce as many stones. Blue slag is most often a robin’s egg blue, but I’ve seen greenish and purplish stones.

Blue slag is popular because of its aesthetic beauty and because it is a very unique and relatively rare type of rock. The type of iron smelting that produced blue slag was phased out in the late 19th century, so little to no blue slag is being created these days.

Related: How To Cut and Polish Blue Slag

However, some glass companies are creating special slag glass varieties that look similar to true blue slag. Many rockhounds, myself included, would instead prefer to scour the shores of Lake Michigan to find original blue slag in the rough.

Read on to learn more about blue slag, including where you can find it for yourself. 

Read More: List Of Minerals And Gemstones Found In Michigan!

What is Blue Slag?

Blue slag originates as various minerals present in iron ore. It is separated from the iron ore during the smelting process, which creates a glassy stone. As blue slag was created in furnaces, it is often pitted with air bubbles created when the molten slag was cooling after being separated from the purified iron ore.

Besides this pitting, however, blue slag is often worn smooth by water. It was common for mining companies to dump the slag into various bodies of water, as it was considered waste.

Blue slag is a relatively soft stone, making it difficult to work with. Its softness also means that it is often found in small pieces despite the enormous quantities produced by old-fashioned iron smelting processes. Even these small pieces are often fractured.

How Is Blue Slag Formed?

The iron smelting process creates many by-products, including blue slag. Blue slag starts out as blue glass impurities within iron ore. The iron ore mined in the Upper Peninsula of Michigan which was processed in the town of Leland was known for having such impurities. 

The Leland Lake Superior Iron Company removed these impurities by smelting, which means heating the iron to incredibly hot temperatures that cause the impurities to separate from the molten iron. While blue glass is responsible for the bluish color of blue slag, other impurities also melted into the blue glass during the smelting process. This is why the color of blue slag can vary from blue to green to purple.

Credit: Library of Congress

When the slag had cooled, it was discarded in favor of the valuable iron ore. The Leland Lake Superior Iron Company originally piled up the blue slag on their property. When they went bankrupt in 1885, they dumped the blue slag into Lake Michigan.

The lesser-known blue slag found in Tennessee and Sweden was also created as a by-product of the iron smelting process.   

Where Can Blue Slag Be Found?

Unsurprisingly, the town of Leland is the most popular destination in Michigan for blue slag hunters. This is where the best-known variety, Leland Blue, can be found. It can also be found in much smaller quantities in Tennessee and Sweden, but of course, these cannot be considered “Leland Blue” slag.

Leland is a small town nestled between the picturesque shores of Lake Michigan and Lake Leelanau. Known for its idyllic location on the Leelanau Peninsula, this historic destination attracts a plethora of visitors during the summer months. Visitors can take in the sights and sounds of people strolling along the sandy beaches in search of Leland blue slag as well as perusing the quaint shops that dot the area.

Beyond The Lower Peninsula

While the lower peninsula of Michigan is renowned for its blue slag deposits, it’s important to note that this phenomenon is not confined to this area alone. The upper Peninsula of Michigan also boasts significant slag finds, underscoring the extensive iron smelting history in the region. This area, with its rich deposits of iron ore, was a hub of smelting activity, contributing to the industrial growth of the region and the nation.

Beyond Michigan, the shores of the other Great Lakes harbor these historical remnants as well. Lake Superior, Lake Huron, Lake Erie, and Lake Ontario were pivotal in the transportation and processing of iron ore, facilitating the establishment of smelters in their vicinity. The strategic locations of these lakes allowed for the efficient movement of raw materials and finished products, making them integral to the smelting industry.

Finding blue slag involves exploring areas known for historic smelting operations. These locations often include old industrial sites, abandoned smelter facilities, and areas near mines. Enthusiasts and collectors frequent these sites, searching for pieces of slag that not only serve as beautiful specimens but also as artifacts that tell the story of a bygone industrial age.

In addition to Michigan and its surroundings, other regions in the United States and around the world where iron smelting was historically significant may also yield blue slag, such as Tennessee. Countries with a rich history of iron production, such as the United Kingdom, Germany, and Sweden, among others, are potential sites for finding slag deposits as well.

For those interested in locating blue slag, it’s advisable to research historical industrial sites, consult with local historical societies, and connect with other collectors and enthusiasts. Safety should be a priority when exploring these areas, as old industrial sites can be hazardous. Moreover, respecting private property and adhering to local regulations is crucial when searching for slag.

Is More Blue Slag Being Produced?

Iron smelting processes have come a long way since the 19th century. Much less slag is produced during the smelting process. Also, iron mining and processing companies generally do not discard the slag they produce in publicly accessible areas.

Modern environmental regulations prevent these companies from simply dumping slag into bodies of water as the Leland Lake Superior Iron Company did in the late 19th century. While this is undoubtedly good for the environment, it also means that rockhounds will not be able to get their hands on freshly made blue slag.

Artificial Blue Slag

The popularity of blue slag from iron smelting operations has led some glassmakers to create varieties of glass that look similar to blue slag. As blue slag is not considered to be particularly valuable, these glassmakers do not attempt to pass off their slag glass as authentic blue slag.

Instead, these glassmakers will use blue-colored slag glass to create a variety of items, including jewelry and figurines. Artificial blue slag glass is easier to work with than genuine blue slag, allowing it to be used for intricate designs that would be impossible with Leland Blue.

Blue Slag is an Important Part of Northern Michigan’s Culture

The famous Leland Blue slag is an important part of the eclectic culture of northern Michigan. There are many rockhounds in the Lower Peninsula who spend hours combing the shores of Lake Michigan for blue slag. There are also quite a few artisanal jewelry designers who create necklaces, bracelets, and other items of jewelry using the iconic blue slag material.

Not only does blue slag play an important part in the lives of many residents of the Lower Peninsula, it is also historically important. The industrial operations that were common in the Lower Peninsula are now long gone, but many of the current residents are descendants of those who moved to northern Michigan in search of the economic opportunities that would give themselves and their families better lives.

Hunting for Blue Slag in Northern Michigan

credit: Kristin Sterkenburg

If you plan on going to northern Michigan to hunt for blue slag, you’re best off focusing on the shores of Lake Michigan near Leland. Most rockhounds who search for blue slag do so by simply walking the beach around the waterline with their eyes on the ground.

Blue slag is easy to spot due to its vibrant color. However, it has become increasingly rare due to its popularity and due to the limited quantities that are accessible. 

Most rockhounds who go to the Lower Peninsula to look for blue slag do so in the summer, as the winters in this neck of the woods are very cold. However, Leland is a popular summer tourist destination, and many of these tourists are rockhounds on the lookout for blue slag. This means that you will face stiff competition if you go looking for blue slag in the summer. 

Local rockhounds often look for blue slag during the winter, when there are fewer people on the beaches. Even if most of the easily accessible blue slag has been picked up during the summer tourist season, more will have washed up by the time winter rolls around. If you can stand the cold, this is the best time to hunt for blue slag.

Blue Slag Jewelry

Blue slag jewelry has become very popular in recent years. In the past, it was only available at small shops in northern Michigan. However, the increased popularity of sites like Etsy and eBay amongst artisanal jewelers means that blue slag jewelry can be purchased from anywhere.

If you’re planning on getting some blue slag jewelry, there are some things that you should keep in mind. First of all, blue slag jewelry often features uncut stones. The softness of blue slag means that it is nearly impossible to cut without fracturing it. Also, not all blue slag jewelry will have the vibrant robins-egg blue color that is often associated with this stone. The stones used in blue slag jewelry often feature varying shades of blue along with purple, grey, and green hues.

Interesting Facts About Blue Slag (FAQ)

Is blue slag rare?

Blue slag is relatively rare, as only a certain type of iron smelting that is no longer utilized produces it. Also, much of the blue slag that was created by smelting was dumped into deep bodies of water.

What are Leland Blues?

Leland Blue is the most common and most well-known variety of blue slag. It is named after the town in which it was created: Leland, Michigan.

How much is blue slag glass worth?

The value of blue slag varies widely based on the appearance of the stone. However, high-quality raw blue slag can cost as much as $100 per pound.

What makes Leland Blue Stone?

As previously mentioned, the iron smelting process employed by the Leland Lake Superior Iron Company produced Leland Blue.

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