Ancient people around the world all made a rather similar discovery.

In certain places they could find a black stone in the ground which could burn.

It was coal.

For the most part, this combustible black rock took a backseat to wood as a fuel source,

but eventually it replaced wood and was the fuel source that drove the Industrial Revolution.

Over time, other energy sources eventually surpassed coal, and now coal appears to be on its way out.

Learn more about coal, its past, present, and future as a source of energy on this episode of

everything everywhere daily. on this episode of at the beginning by explaining exactly what coal is.

Coal is a black sedimentary rock that was formed geologically from dead organic matter.

The way it was believed to have been formed was from vast swamp forests that covered most of the Earth during the late

Carboniferous period from about 300 to 323 million years ago. These swamp forests were, as the name would suggest, large swampy areas with dense tree growth.

As plants died, they fell into the muddy water where they couldn't oxidize and decay.

Eventually, this layer of organic matter built up and was covered by more

sediment layers. Over time this layer of organic matter would become what's known as

peat, which in and of itself is a combustible fuel source.

But after further compression by more sediment over millions of years,

water, methane and carbon dioxide would be expelled,

leaving a denser rock with more carbon.

Coal is a rock, but it's not a mineral,

so there isn't a single chemical formula for coal.

There are different types of coal based on the geological processes which acted on it. Roughly speaking

there are four grades of coal. The lowest grade of coal is called Lignite.

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