How Are Minerals Formed?

Minerals form in slightly different ways which I will explain below, however one thing is common about their formation - there is a change in conditions in the surrounding rock, in which the new mineral is more stable than whatever substance, or another mineral, it was formed from.



While plants and animals strive to save energy which is consumed by growth, movement etc.., rocks and minerals also have an issue with energy and stability. 

As you probably know, mineral crystals don't only form but also grow. And exactly like with animals, it takes them energy to grow.

 
 How are minerals formed. ©collecting-rocks-and-minerals.com

They don't "want" to spend that energy, they all strive to achieve the total stability of noble gases (the gases in the last column in the Periodic Table - He, Ne, Ar, Kr, Xe, and Rn - the gases that never react with other elements, because they are so stable that they don't need to).

Minerals are obviously not living things, so why do they grow? The only reason why mineral crystals grow is that by growing, they get more stable (even though they use energy while growing). In other words, the strival for stability drives them to put on another layer, and another layer, and another layer, because the larger they are, the less surface they have relative to their volume. And surface is the unstable part of a mineral.

For exactly the same reason, chemical elements react and minerals form - the product of the reaction is more stable than the reactant was.

The things involved with mineral formation are changing pressures, temperatures, and often, liquids in hydrothermal veins.

 
 How are minerals formed. ©collecting-rocks-and-minerals.com

Both pressures and temperatures increase with depth in the inner Earth. So as a mineral is moved deeper down, it will come to a stage where either pressures or temperatures, or both, have increased so much that the rock will deform, chemical reactions will happen, and new minerals are formed.

In igenous processes, the previous rock is first molten into magma, and minerals only form once the magma cools again when it either gets closer to the surface (intrusive igneous processes), or erupts out of a volcano (extrusive igneous processes). In metamorphic processes, mineral changes happen in solid state - there is no melting. In some metamorphic processes, only heat is involved (contact metamorphism). In other, both heat and pressures are involved (regional metamorphism).

 
 How are minerals formed. ©collecting-rocks-and-minerals.com

Hydrothermal veins are veins filled by minerals such as quartz. Originally there has been a fault, or a fracture along a joint, and minerals often fill those veins. Often, hot hydrothermal liquids, mainly water, are involved, so again, there are changes in conditions, such as temperatures. Those veins are also known for ore mineralisations.