Sometimes it is from iron-metabolizing bacteria.
They were here long before both Gore and "Talking Bull".
Isn't that the stuff them Indians rebels on Alcatraz put in the San Francisco drinkin water back in the 1970's when Russel whathisname was out here?
That stuff is potent! It's made a whole city try to justify some of it's preverted "in your face" behavior as some kind of stupid "civil rights movement!"
Course, if ya ask me, it's just a real sickening vowel movement!!!