Scientific flash - N° 2 - Please don't say that coal is a mineral - ¿What that hell is a mineral?

in science •  last year

Hello fellas ;) <3!

I hope you are all doing well! :D.

Today I bring you a scientific post focused on the common mistake that some people do, and this is referred to the wrong use of the word mineral in a geologic context

The first example that I bring you and maybe the most alarming is related with the word Coal, because a lot of people (even geologist) say that coal is a mineral (¿WTF?), and this is totally incorret, because coal is a rock and it can't be called mineral, for the simple reason that it doesn't fit in the definition of mineral, which is:

¨A Mineral is a body produced by the processes of inorganic nature, having a definite chemical composition and, if formed under favorable conditions, a certain characteristic molecular structure which is exhibited in its crystalline form and other physical properties.¨ (Dana, E. 1997)

What a beautiful coal <3, ¿isn't it?

So with this concept on mind, we can understand that a mineral has to have at least three characteristics:

  • Be originate by a process of inorganic nature (not organic)
  • It has to have a definite chemical composition
  • It must to have a molecular structure defined (crystalline structure)

Therefore coal can't be called mineral, because their origin is related by organic process.


Another example that I bring is related to obsidian or volcanic glass, which is wrongly called mineral, because this material is also a rock.

In this case, the reason that obsidian doesn't fit in the definition of mineral is because this one doesn't has a molecular structure defined, so it lacks of a crystalline structure; in addition, its composition is too complex to has a definite chemical composition.

Look at these beautiful obsidians <3

Then, we have to be careful with the use of the mineral concept, and think about origin, estructure and chemical composition of the material before call it mineral ;)

I really hope that you enjoyed this post!


PS: Another cool quote!

Geologists have a saying - rocks remember. Neil Armstrong

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