WATER DOES STRANGE THINGS deep within the crust.
The deeper you go the hotter it gets and the deeper you go the higher the
pressure from the overlying rocks.
Imagine having a kilometer of rocks pushing down on you!
Under the influence of high pressure / temperature water becomes a SUPER
SOLVENT and CAN EASILY DISSOLVE MINERALS.
Given high enought pressure / temperature water can even dissolve gold!
So in order to grow crystals the water must slowly either COOL or LOSE
PRESSURE or BOTH.
The longer this takes to happen the bigger the crystals.
The name HYDROTHERMAL liquid is give to the hot mineral rich water under
Open space filling by warm water at lower pressures creates EPITHERMAL
vein systems, a common source of crystals and some valuable metals.
In this specimen a cavity is filled with low temperature mineral saturated
The water enters a cavity (hole) in the rock.
The bigger space means the water loses pressure and the dissolved minerals
slowly come out of the water to form crystals.
As the fluid cools the dissolved quartz mineral preciptates and forms
The crystals grow out at right angles from the cavity wall.
The larger the crystals, the longer the period of crystallisation.
We can now grow gemstones in a factory
but the because of the high pressure and high temperatures...
the process is expensive.