A crystal system characterised by the presence of a hexad (axis of 6-fold rotation). Two of the axes are 120deg apart and are of equal length. The third axis (c) is aligned with the hexad, and is 90deg to the other two axes.

These crystals are usually shaped like six-sided prisms or pyramids. Each crystal has four axes of symmetry. Three lie in the same plane, are the same length, and intersect at 120° angles. The fourth axis is not the same length, and is perpendicular to other three. Example: beryl

(hex-ag´-o-nal) One of the six crystal systems, characterized by one unique axis of threefold or sixfold symmetry that is perpendicular and unequal in length to three identical axes that intersect at angles of 120°. This definition includes the trigonal system.

A plane figure having six sides and six angles.

Polygon having six angles and six sides.