A percussion figure is a flat, six-rayed "star" formed when hexagonal micaceous minerals are put under pressure. The "star" is composed of six lines protruding from each corner of the crystal that bisect near the center of the crystal. A percussion figure seen on a mineral proves it to be a mica or related mineral. Pushing a thin needle into the center of the crystals may artificially create percussion figures. This will only work if the crystal is:

• Hexagonal shaped
• Has a smooth, flat surface
• Has no flaws or cracks

• Mineral Properties
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