What is a MINERAL

A mineral is a substance that is:

• Natural - it is not man-made
• Inorganic - it is not alive
• Solid - it exists as a solid
• Possess an orderly internal structure of atoms (aka crystal lattice) - the elements that comprise the mineral are ordered in a predictable, repeatable pattern.
• Has a definite chemical composition - the elements that comprise the mineral are always the same.  
  

 

What is a mineral, and what isn't?

-	-	Naturally Occurring	Solid	Inorganic	Crystal Structure	Chemical Composition
Mineral!	Ice	✓	✓	✓	✓	✓
	Water	✓	-	✓	-	✓
	Bones (living)	✓	✓	-	✓	✓
Mineral!	Bones (fossils)	✓	✓	✓	✓	✓
	Coal	✓	✓	-	✓	✓
	Steel	-	✓	✓	✓	✓
Mineral!	Quartz	✓	✓	✓	✓	✓
	Opals	✓	✓	✓	-	✓

Why are ice, fossilized bones, and quartz considered minerals, while the others are not? Let's look at each individually.

• Ice - Ice occurs naturally, is inorganic, and is a solid. It has an ordered chemical structure and unique chemical formula (H₂O)
• Water - Water is a liquid, not a solid.
• Bones (living) - Living bones are organic.
• Bones (fossils) - Fossilized bones can be considered a mineral. After death, the bones get burred, and minerals within the groundwater start to replace the cells in the bones, fossilizing them.
• Coal - Coal is made from the remains of plants, and is therefore organic.
• Steel - Steel is an alloy, a combination of carbon and iron, and therefore does not occur naturally.
• Quartz - Quartz occurs naturally, is inorganic, and is a solid. It has a ordered chemical structure and formula (SiO₂)
• Opals - Opals meet almost all of the criteria with the exception of the ordered chemical structure. Instead of an orderly internal structure, the elements that comprise opals are disorganized.

The crystalline structure of a mineral is based on atomic patterns. Atoms in a mineral are specifically ordered (example: square, circle, triangle, square, circle, triangle). A solid with disordered atoms is called a glass.

Opals are an example of a mineraloid; they meet all of the other criteria, but lack an orderly internal structure.

Polymorphs are minerals that have the same chemical composition but form different crystalline structures.

Example:

Mineral	Diamond	Graphite
Chemical Formula	C	C
Structure	Each Carbon atom is bonded with the one next to it.	Each Carbon atom is bonded to the next in layers
Bonding	Strong covalent bonds; hardest mineral	Weak Van der Waals bonds; softest mineral

 

Out of the 92 naturally occurring elements, only eight of them are common in most rocks. They are:

Element	Chemical Symbol	Percent Weight in Earth's Crust
Oxygen	O	46.60
Silicon	Si	27.72
Aluminum	Al	8.13
Iron	Fe	5.00
Calcium	Ca	3.63
Sodium	Na	2.83
Potassium	K	2.59
Magnesium	Mg	2.09