Some crystal beads used to make bracelets are partly discolored. How do you remove the discoloration?

You wear it and it’ll come off. My mom has these amythest/crystal bracelets that sh used to wear all the time but then later she stopped wearing them and when she put them back on they had some parts that were kinna brownish. She wore them for like a week and the brown spots disappeared.

Crystal Beads Bracelet
Crystal Beads Bracelet
Crystal Beads Bracelet