Korialstrasz69
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Hard crystals
As far as i know grown crystals are usually fragil and break easly.So two questions :
I think real crystals are made undet high pressure and temperature,right ? Is there no salt that doesn't require these conditions to grow hard ?
Is there some sort of resistant transparent coating to apply to crytals ?because some might becme black with time i think due to oxidation.
Thanks ahead
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crystal grower
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1.) They're all "real" crystals, doesn't matter whether they were made by cooling the solution, vaporisation, CVD,....
2.) Crystals crystalized from water ussually contain water molecules in their crystal lattice which make them prone to dehydratation/make them
fragile.
However NaCl, KCl doesn't form hydrates so they won't dehydrate. But they aren't very hard (~2 mohs scale).
From my personal experience, crystals of cuso4.5h2o aren't very fragile and are a little harder than crystals of Nacl. The problem is again in
dehydration.
There are two ways how to store them:
-place them into closed box
-or cover them with transparent nail polish.
Very nice crystals of moderate hardness forms bismut
(procedure: http://chem.pieceofscience.com/?p=884 -here you can also find anothec crystal growing procedures.)
[Edited on 2-4-2016 by crystal grower]
[Edited on 2-4-2016 by crystal grower]
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deltaH
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The hardness of a crystal has a lot to do with the strength of the bond between the units that make up the crystal.
Going from weakest to strongest:
(1) Van der Waals forces only.
This is typical or organic crystals. Discrete covalent molecules where adjacent molecules are held in place by weak Van der Waals forces only. These
are easily disrupted by even the weakest of non-polar solvents.
(2) Ionic crystals. NaCl etc. Stronger ionic bonding, also results in harder crystals but can be solvated by strongly polar solvents like water.
(3) Covalent crystals. e.g. Diamond. The very strongest of crystals are those where strong covalent bonding occurs between adjacent atoms throughout,
linking all atoms to all overs covalently, i.e. there are no discrete covalent molecules to speak off.
In between (2) and (3) are materials with varying degrees of covalent and ionic character. This is where most gemstones fit in.
[Edited on 2-4-2016 by deltaH]
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