Artificial changoite, formula: Na2Zn(SO4)2·4H2O Double sulfate of zinc and sodium. Natural variety of this compound is known as mineral сhangoite.
- Crystal system: monoclinic.
- Crystal shape: tabular, with striations on sides
- Stability on air: stable
Dissolve equimolar amounts of sodium sulfate (usually Na2SO4·10H2O) and zinc sulfate (ZnSO4·7H2O) in water, then crystallize. The compound is very soluble, so water should barely cover solid salts.
I used regular slow evaporation method. This copound has good solubility (my very rough guess - between 50 and 100 g per 100ml), so evaporation should not be too fast.
Mostly safe, though in significant amounts zinc can be toxic.