1. Place a small amount of powdered mineral in a platinum crucible and add concentrated sulfuric acid, then heat the crucible gently over a lamp, candle, or Bunsen gas burner, now place a wax-coated glass plate that has been scratched over the crucible; the exposed portions of the glass where the wax has been scratched away will be etched and corroded by HF fumes produced by the reaction.

2. Mix a small amount of powdered mineral with some powdered glass and three times as much potassium bisulphate (KHSO₄), place the mixture in a closed tube and gently heat it with a lamp, candle, or Bunsen gas burner; a white sublimate will form in the tube accompanied by corrosive fumes of HF gas which attack and etch the glass.