Sodium Chloride

Table salt. Formula: NaCl

Table salt is probably the most available component for growing crystals. It is also one of the hardest components to grow. I made countless number of attempts, and only one of them produced fine results, presented here. You are lucky if you can get clear, well-formed 5mm, salt crystal. If you get 10mm, it is success. And if you manage to get a bigger one, then please tell me how you did it.

Properties

Crystal system: isometric
Crystal shape: cuboid
Color: colorless
Stability on air: very stable

Growing

NaCl is prone to forming Hopper faces. You'll get dendrites, white crystalline crust, hollow flat rectangles - anything but not the transparent cubes. NaCl also crystallizes too readily, using every smallest crack or dust particle as a seed.

So, without some trick you'll never get big and transparent crystals. I'd like to share a trick I have found by an accident. Not sure that it is the best method for growing NaCl crystals at home, but it worked for me, at least.

The trick was to use not the pure NaCl solution (as it is usually recommended), but a mixed solution of salt and iron (III) chloride FeCl3. It is used by amateurs in the printed circuit board production, and can be bought in the most shops for electronic hobbyists.

By some mysterious reason, presence of FeCl3 changes the way salt crystals grow: they are growing bigger and more transparent. Iron chloride itself is not going into the crystal, though occasionally small portions of the ferrous solution are getting included in the transparent crystals, creating yellow spots inside.

Still, crystal growth is not fast. In my case, growing centimeter-size crystals required about 6 months.