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Blue Slag (What Is It and Where To Find It)

where to find blue slag stone

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.

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 Superior 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, especially around 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 Superior.

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?

Most of the blue slag can be found on the Upper Peninsula of Michigan in the United States. 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.

Unsurprisingly, the town of Leland is the most popular destination in Michigan for blue slag hunters. However, blue slag is also known to wash up on the shores of Lake Superior in towns near Leland. 

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 more 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 Upper Peninsula who spend hours combing the shores of Lake Superior for blue slag. There are also quite a few artisanal jewelry designers who create necklaces, bracelets, and other items of jewelry using blue slag.

Not only does blue slag play an important part in the lives of many residents of the Upper Peninsula, it is also historically important. The industrial operations that were common in the Upper Peninsula are now long gone, but many of the current residents are descendents 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

If you plan on going to northern Michigan to hunt for blue slag, you’re best off focusing on the shores of Lake Superior 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 Upper 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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