Geology 04 - The formation of minerals

The key word here is crystallization.


(Source: image is from the video at the bottom of the post)

There are mainly 3 ways minerals are formed.

1.When magma become cold, and different minerals there gather and crystallise.
2.When lakes dries out, and leave a lot of mineral rich deposits and this crystallises
3.when water are captured under the ground and become heated and then cool down, then the minerals gather and crystallises.

Crystallisation by evaporation above ground:

(Source: image is from the video at the bottom of the post)

Many places have been covered with ocean. And when this water disappear they leave a rich mineral solution behind.
Then this solutions start to crystallise.
We can also see this easy if we look at those who produce salt with salt pools.

(Image source: http://www.marisol.biz/en/sea-salt/artisan-salt-production.html)

Magma:
In molten material like magma(that is melted minerals) the atoms tend to find each other.
So when the magma get cool, this minerals start to crystallise.

(You can actually buy small kit for children to grow crystals, and then you will see this in practise, in this kits you need to boil the water first, and then cool it off in your refrigerator or something. and just after 2-3 days you clearly see the crystallisation and big visible crystals start to grow. This kits are usually salt crystals)

(Source: https://www.amazon.com/Scientific-Explorer-Ultimate-Crystal-Growing/dp/B000ESWFA6)

In general you can say that the faster it cool of, the smaller the crystals become.
The crystals formed deep in ground where it use longer time to cool off, usually become much bigger because of longer crystallization time.

This you can see clearly in 2 types of rock, that are made of the same 3 basic minerals(quartz, hornblende and feldspar), Granite and Pegmatite.
Granite: Pegmatite:

In granite there is small crystals that make the rock, but Pegmatite is the same rock that have been cooled of much slower,
and therefore the crystals in Pegmatite is much bigger.

For the same reason, most mineral/crystal collectors become very exited and curious when they see a Pegmatite vein in the mountain, and will want to take a closer look at it.

This is how a Pegmatite vein in a rock often look like. (Source: https://qrius.si.edu/browse/object/10018837#.WdnCjYO7WUk)

Underground water crystallization:

(Source: image is from the video at the bottom of the post)

When water are captured under ground and get heated, for example by magma veins close to it, it attracts minerals around it and it become a rich mineral solution in it.
If the same water then cool of, this minerals will then crystallise.

(Source: https://lifeinthefastlane.com/the-crystal-cave-naica-mexico/)
If the same water for different reasons find a way out, we will then have a cave full of crystals, like for example the famous crystal cave found in Naica, Mexico not so very long ago in the picture above.

Most of this you can also see in this short video:

(Source: Harinder Singh - Youtube)