Will Coal Set Off a Metal Detector: When Science Meets Scrooge

  • By: Chris
  • Last updated on February 4, 2023
  • Time to read: 5 min.
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Well, Bah Humbug!

Here you are, trying to figure out if your metal detector actually picked up coal. 

Or, dare you hope it’s really volcanic rock you uncovered?

Sorry to disappoint you. It could very well be the coal you feared.

The prevailing amount of carbon within a piece of coal will definitely set off a metal detector.

But that doesn’t have to be an automatic bummer!

finding coal isn't a bummer
It’s not as bad as you think. Coal has its uses.

If you’re like me, the details matter in everything. 

So keep reading, and you’ll soon learn why this happened. And I’ll tell you whether it’s a worthwhile surprise you stumbled upon or a waste of time.

Will a Metal Detector Pick up Coal?

No matter the type of coal, a metal detector will pick it up because carbon, which makes up more than half of its weight, is an excellent conductor of electricity.

I’ll keep it simple and briefly explain if you’re unfamiliar with the inner workings of a metal detector.

A metal detector picks up on metals and other objects, like rocks, that are good conductors of electricity. 

will a metal detector pick up coal carbon inside
Because of coal’s carbon makeup, a metal detector will have no problem picking it up.

Some elements are better conductors than others, like carbon. And the better conductor an object is, the more it interacts with the magnetic field of a metal detector.

By interact, I mean that it disrupts the field generated by the detector, which causes an alert for the Digger using it.

But what’s so special about coal anyway? 

What’s stopping you from simply tossing it aside? 

Patience, my fellow dirt fishing enthusiast. 

(Or ruin the surprise and skip to the end.)

don't ruin the surprise of coal
I get it; you want your answers. Be stick with me here.

You might imagine some old soot-covered Kentucky miner when you think of coal, and you wouldn’t be wrong.

Just don’t be surprised to find it during your metal detecting adventures. It’s used in one form or another just about everywhere.

What Is Coal Used for Today?

Coal has significant advantages, and despite the environmental concerns, so many industries find uses for coal in today’s world.

The most crucial advantage of coal today is it’s the number one most comprehensive electrical source in our economy.

Coal-derived fuels are a sought-after global resource in gas or liquid form.

what is coal used for today
Coal has a crucial role in our present-day world from fuel to electronics.

Other well-known uses of coal and its byproducts today include being the primary element in creating durable alloy metals, manufacturing electronic circuitry, carbon fiber, solar panels, and concrete production.

I can imagine you thinking, “that’s great and all. But why am I finding coal? And why have I still not tossed it?”

Thanks for not skipping ahead.

So, you now know that carbon is the leading reason a metal detector is set off by coal. But what else will you find in these black rocks?

Are there any other valuable metals or elements you can benefit from?

And if there is, where can you find more of it?

Well, let’s talk about it.

let's have a talk
It’s a good time for a conversation about coal.

Is Coal a Rock or A Mineral?

Coal, in any form, is classified as a sedimentary rock made of different minerals through a long geological process.

It’s generally black with occasional brownish tones and hard to the touch.

What Is Coal Made From?

Despite carbon being the primary component, coal is also made from a mixture of sulfur, oxygen, hydrogen, ash, and nitrogen.

The way that coal forms can be complicated.

formation of coal
The formation of coal in a 4-step diagram.

But in essence, generations of plants that have died and fallen into swamp water were left to decay. Each new plant lifecycle added more fallen plants to the rotted layers.

Given enough time, sudden environmental instabilities lead to increased pressure and tremendous changes in temperature.

When this occurred, peat, a low-carbon organic decay, transitioned into coal by expelling oxygen for more carbon.

Well, that was a mouthful! 

Here’s a helpful video to simplify it better than I can.

How Long Does Coal take to Form?

If you’ve found coal while metal detecting, what you’ve really discovered is a bit of history.

Coal takes an incredibly long time to form. In fact, a relatively bountiful coal seam will take millions of years to develop, at a minimum.

According to coal geologist Dr. Judy Bailey, peat, the precursor to coal, can take anywhere from 12,000 to 60,000 years to form a three-meter coal seam.

That’s less than ten feet!

But that’s only the peat. Factoring in that additional million-plus years is for the peat to change into coal.

Where Can Coal be Found?

where can coal be found
Five states produced the bulk of US-sourced coal in 2021.

As I mentioned earlier, coal can be found just about everywhere.

For the US, official coal production happens in roughly half the states. 

But amazingly, 74% of the entire US coal production in 2021 derived from only five states; Wyoming, West Virginia, Pennsylvania, Illinois, and Montana.

Finding coal might not be so random if you’re from these mountain areas.

So keep your eyes peeled, and keep your metal detector charged.

What You Really Want to Know: Is It Valuable?

Ok, you sat through a whole lot of details. Congrats!

But why?

frustrated tell me why
Ok, ok. You’ve waited long enough.

Earlier I mentioned the other elements you’ll most likely find in coal. Last time I checked, sulfur and ash have little value.

So why care about where to find coal, how it forms, and what it looks like?

What’s the payoff I promised?

It’s simple.

It doesn’t happen all the time, but there are confirmed cases of precious elements like gold and diamonds being found in coal and coal low temperature ash (LTA).

The last thing you want to do is throw away a literal ‘diamond in the rough‘ like you ended up on Santa’s naughty list.

So next time a piece of coal sets off your metal detector, hold on to it for later when you can inspect it.

In the best-case scenario, you found yourself a little treasure.

I hope the wait was worth it.

Until next time, Diggers.

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