Elemental potassium is a soft silvery-white metallic alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the evolved hydrogen. Potassium in ... As such, it is found dissolved in seawater, and as part of many minerals. ... Elemental potassium does not occur in nature because it reacts violently with water (see section Precautions below). ... Figure 140: Potassium in feldspar Kilogram quantities of potassium cost far more, in the range.