Such quartz crystals form when right and a left hand quartz structures are combined in a single crystal. Think of a stack of sub-microscopic quartz crystals that stack so that their “c” or optic axis is perpendicular to the direction of stacking and each successive sub-microscopic crystal is twisted a bit from its predecessor. The overall twist of these quartz crystal fragments can be either a twist in a counter-clockwise direction, which is a ‘right-handed twist’ or it can twist in a clockwise direction, which is a ‘left-handed twist’.