A chemical indicator has been added to the water, partly to show the trail of the sodium as it moves across the water, and also to show what happens as the sodium reacts. The indicator is colourless unless the solution becomes alkaline, in which case it turns bright pink. The heat released causes the metal to form a rolling molten ball. Notice that the water has turned bright pink. Thealkaline reaction causes the phenolphthalein indicator to turn pink.
Sodium is present in the white and pink feldspar crystals in a piece of granite.
When volcanic rocks decompose they release sodium. Sodium compounds are found in all the freshwater rivers and lakes of the world in tiny amounts. But when the lake dries out, the sodium compounds are left behind. Crystals of salt are soft and easily scratched. They are mostly white, although they may be tinged with orange if they have some iron staining.