Most dancers are quite familiar with the “Aurora Borealis” crystals. This is in fact, a special coating over regular [clear] crystal that gives it that shimmering iridescent multi-coloured effect. Of course, you can have other colours coated with “AB” as well which changes the stone appearance. But what you see most in ballroom is Crystal AB – the clear crystal with the AB coating. In fact, it’s so popular, it’s pretty much considered a neutral stone colour.
(I suppose only a ballroom dancer would consider something super sparkly as a “neutral” haha!)
Many crystal manufacturers have their own magical [likely secret] formula for their AB coating. This vacuum-sputtered metallic coating was in fact a joint effort creation when Swarovski and Christian Dior wanted to develop a rainbow stone. Beginning in 1953 and perfected by 1955, this amazing process has become a much-loved crystal colour, arguably the most frequently used stone colour choice in the world of dance.