The team's invisibility cloak exploits this effect, and relies on a specific geometry comprising two prism-shaped calcite crystals glued together, such that they leave a wedge-shaped gap beneath in which objects can be "cloaked" when illuminated with polarised light.

BBC: Invisibility cloaking benefits from crystal-clear idea

It had a big gap down, formed a wedge, and then it came down hard again, falling 98 cents to 26.51 on Monday.

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After falling in a multi-week wedge, it exploded with a big breakaway gap, up 5.34 to 36.80, or 17%, on 7.4 million shares.

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