Potassium
K
atomic number
19
melting point
63.38°C

1. Heat a very small mineral fragment (using forceps or tweezers) or a bit of powdered mineral (using a platinum wire loop) with a hot flame using a lamp, candle, or Bunsen gas burner; potassium (and sodium, which is almost invariably present) impart a pale violet color to the flame; viewed through a blue glass filter (which eliminates the sodium flame color), the flame will take on a violet or purplish-red color; (potassium-bearing silicates must be powdered and mixed with finely pulverized gypsum before performing this test).

2. Heat a small mineral fragment (using forceps or tweezers) or a bit of powdered mineral (using a moistened platinum wire loop) with a very hot flame using a lamp, candle, or Bunsen gas burner, then dab a bit of the sample onto a strip of moistened turmeric paper; many potassium-bearing minerals will give an alkaline reaction.