After forming a white substance while on the stove, I rinsed the Pyrex pot under tap water (from a well), whereupon the water in the pot turned purple. Why did this happen?
Iron and sulfur are present in the well water here.
Revision: I had prepared white tea in a white corning pot on the stove. After pouring out the tea I rinsed the pot with the tap water (well water) which turned a purplish color and then clear.