“All that glisters is not gold,” Shakespeare wrote in The Merchant of Venice. If not gold, what else could “glister,” or as we would now say, “glisten?” Mica particles could have come to mind. This silicate mineral readily fragments into thin sheets that can be ground into fine, shimmering particles. Already aware of this some 30,000 years ago, Paleolithic cavemen blended mica flakes with hematite (iron oxide) to give cave paintings a shimmering appearance. Ancient Egyptians powdered the green mineral malachite to make eye makeup sparkle, and also made use of iridescent beetle shells to add glimmer to cosmetics. But the bard would not have known about “glitter,” the tiny reflective particles that today adorn greeting cards, toys, fingernails, inks, decals, festive items, cosmetics and fishing lures.
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