Azure ingots for Christmas

This picture will be very familiar to many, as it shows some distinctive crystals of copper sulphate. They are known due to their very characteristic deep blue colour and their oblique rectangular formations.

Copper sulphate in this form is pentahydrate; the coordination with water molecules is what gives it its colour and its triclinic crystal structure, while its anhydrous form is white and orthorhombic. Both of them have an interesting range of applications, and although their toxicity makes them inferior to other compounds it is useful when developing herbicides and pesticides. 

Yet of course, its toxicity is very low and it will not keep away many amateurs like myself to try to demonstrate some chemistry principles or just to grow a couple of lovely blue crystals at home during Christmas holidays. Merry crystal growth!

Author: Sergi Batlle