They are chemically the purest of all diamond crystals and often have extraordinary optical transparency.

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These types of diamonds are the most chemically pure, lacking in nitrogen which therefore yield exceptional optical transparency.

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An optical laser reads the transparency and creates a wobbly, out-of-tune, almost eerie-sounding keyboard effect.

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The Optigan, or optical organ, plays samples from a transparency with sound waves printed on it, like the grooves on a record.

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