# Could you form quartz crystals by melting and cooling sand very slowly?

Since glass is amorphous quartz and when you slow the cooling of something enough it will crystallize, couldn’t you melt $$\ce{SiO2}$$ (sand) and then very slowly cool it to cause spontaneous nucleation and form quartz crystals?

If so, then why hasn’t it been used before? It would seem to be a better method than flux because in flux you need many chemicals and a dissolving chemical or mix and it is a complicated and very long process to grow very small crystals throughout the whole mix. If you simply cooled a molten mixture slowly enough to cause complete crystallization, then the entire mix of molten crystal would need to form crystal because it all is cooling down.

• About the second part of your question, both the α- and the β-phase of quartz have what we call an enantiomorphic space group. It forms spirals that can be 'enantiomers' to each other, which I guess also gives it its properties. For many applications you often need the pure enantiomer which will grow in a seed of the correct orientation under for example hydrothermal conditions. May 27 '19 at 8:27
• Melting and cooling will give you a bunch of crystals lumped together. Why would you want that? Then again, I've seen single crystals of quartz as big as a tabletop, and they were not made by melting. May 27 '19 at 8:29
• May 27 '19 at 8:47
• In principle, maybe. But that isn't how big crystals are formed in nature. Most deposit from solutions not from melted pure silica. May 27 '19 at 13:03
• @NightWriter Your example post is about hydrothermal growth of a crystal. May 27 '19 at 21:37