Types and Varieties of Coal

Coal is kind of interesting when you look at it through the lens of a rockhound. I don’t know about you but I’ve never gone digging for coal or filled a 5-gallon buck full of coal to take home with me. I’ve also never put one on a dop stick to cut a cabochon or facet a gem.

So why would I spend time educating a bunch of rockhounds on coal? For one, it’s been used for centuries and archeologists found evidence that the Romans in England used coal during the second and third centuries.

By the 1700s, the English realized that coal could produce hotter and cleaner fuel than wood charcoal.

Let us take a moment and educate ourselves on one of the most versatile rocks, humans have ever found.

 

Types of Coal

It may not be evident to some, but there are a few different types of coal. Coal is different from other rocks and minerals because it derives its origin from organic materials. This material is comprised of fragile plant matter and undergoes various changes before it becomes the familiar shiny black substance many of us use.

Let’s dig in!

 

 

Anthracite

Anthracite is the best coal money can buy. It contains the most carbon, up to 97%, meaning it has the most energy. It’s harder, denser, and more lustrous than the other types of coal.

What makes it so unique? For one, nearly all the water and carbon dioxide are expelled from it, and it doesn’t contain the fibrous or soft sections seen in Bituminous or Lignite coal.

Because Anthracite is of high quality, it burns clean with very little soot. However, it comes at a cost because this is the most expensive variety of coal.

 

 

Lignite

Lignite coal is the bottom of the barrel, the lowest rank of coal because it comes from relatively young coal deposits, about 250 million years old. It’s carbonized beyond being peat, but it contains low amounts of energy (25 to 35 percent). 

The one thing you’ll notice when you handle lignite is its crumbly appearance and the overall color is more brown than black. If you work in the coal industry then you’d call lignite rosebud coal or brown coal.

It retains more moisture than other coal types, which makes it more expensive and dangerous to mine, transport, and store. Lignite is susceptible to accidental combustion and produces a very high carbon emission when burned.

The number one use for this type of coal is in power stations close to the original mine sites.

 

 

Bituminous

Bituminous coal is formed under more pressure and heat than other types of coal and is 100 to 300 million years old. It’s named after the sticky, tar-like substance called Bitumen that’s also found in petroleum.

This type of coal has a carbon content between forty-five and eighty-six percent.

It often contains strips or bands of different consistencies that mark the layers of plant materials that were compressed during its formation. This type of coal is divided into three major types: Cannel coal, Smithing coal, and Coking coal.

Smithing coal produces a very low ash content and is ideal for forges, hence the name Smithing coal. 

Cannel coal was used extensively as a source of coal oil during the 19th century. This oil is made by heating the coal with controlled oxygen.

Here’s a cool fact about Cannel coal – It was used primarily to fuel streetlights and other forms of illumination during the early 20th century.

Coking coal is used primarily in large-scale industrial processes. This type of Bituminous coal is coked, a method of heating the coal in the absence of oxygen which reduces the moisture content, making it a more stable product.

 

 

Sub-Bituminous

Sub-bituminous or Subbituminous coal is around 100 million years old and contains more carbon than Lignite. In many regions of the world, this type of coal is considered ‘brown coal,’ along with Lignite. Similar to Lignite, Sub-Bituminous coal is primarily used to generate electricity.

Most of this type of coal in the US is mined in Wyoming and makes up around 47% of all the coal produced in the United States. Outside of the US, China is a leading producer of Sub-Bituminous coal.

 

Is Coal A Mineral?

Coal is known to have originated from biological sources, meaning it is not categorized as a mineral. It is believed that coal was generated from the remains of dead plants and animals deep beneath the Earth’s surface, where the plant and animal remains were exposed to high pressure and temperatures for extended periods.

 

 

Where Is Coal Found?

Coal is primarily found in three regions: the Interior coal region, the Appalachian coal region, and the Western coal region (which includes the Powder River Basin). The two largest mines in the United States are the Black Thunder and the North Antelope Rochelle mines in Wyoming.

Coal exists in underground formations called “coal beds” or “coal seams.” Coal seams can be as thick as 90 feet and stretch 920 miles.

In the US, coal is mined in 25 states within the three significant regions mentioned above. Wyoming is the top producer in the Western Coal Region, with about 40% of the coal mined in our country being extracted from that location. Over one-third of the nation’s coal comes from the Appalachian Coal Region, including Virginia, West Virginia, Tennessee, and Kentucky.

Coal extracted from Texas in the Interior Coal Region mainly supplies local markets.

If you’re looking to add a couple of pieces of coal to your collection and you don’t live in one of the states mentioned above then here is a cool way to find some coal in your neck of the woods. You can typically find chunks of coal beside railroad tracks where coal is hauled on transport trains from state to state. Happy hunting!