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[Minerals & Fossils yt]

Here is a simplified guide which gives a brief guideline of hydrogen as an element and how it appears in minerals (in its most common forms!)

[Roger Warin]

Hello,
Water exists everywhere in space because it is the result of the combination of hydrogen from the Big Bang with one of the most abundant elements, oxygen.

On Earth, it was captured in minerals, in the form of OH radicals as in amphiboles, or molecules trapped by cations (coordinated ligans). The whole constitutes an ocean. In addition, the Earth captured water from primitive (cold) meteorites and comets during the great bombardment, around – 4 billion years ago. It's good for Pastis.

[Minerals & Fossils yt]

Great info! Thanks for adding more interesting info to this topic!

[alfredo]

An interesting experiment is to take a mineral that contains a lot of water in its formula and is also very soluble, like epsomite for example, and warm it. The mineral is apparently dry and solid in its natural state, but when warmed up it releases some of its bound water and then fully dissolves in it, turning into a puddle. A viewer might think the mineral has "melted", but technically it didn't melt, it dissolved in its own water. Consequently such minerals are best kept in the refrigerator, as most collectors don't want liquid puddles in their collections.

[Roger Warin]

The simplest examples are the least understood by amateurs.
The little chemist at school is often surprised by the formula of plaster, an industrial derivative of the dehydration of gypsum. How can you make a crystal with half a molecule of water?
CaSO₄. 2 H₂O + temperature → CaSO₄ . ½ H₂O (plaster) + T → anhydrite CaSO₄.

These 3 compounds are IMA validated: gypsum, bassanite, anhydrite.
I believe that very few collectors know about bassanite from Monte Somma, Italy.
This means that the water molecules of crystallization can be very differently "attached" in the crystal.