Of or pertaining to a tetragon; having four angles or sides; thus, the square, the parallelogram, the rhombus, and the trapezium are tetragonal fingers.
Having four prominent longitudinal angles.
Designating, or belonging to, a certain system of crystallization; dimetric. See Tetragonal system, under Crystallization.
A crystal system where two of the cell sizes are equal (a & b) whilst the other (c by definition) is of a different length. All inter-axis angles are 90deg. This has one tetrad (axis of 4-fold rotational symmetry) and no triads (axes of 3-fold rotational symmetry), but does have 2 diads (2 fold rotational symmetry). By setting the length of c to that of a&b, the system becomes cubic. By setting a, b, and c to different lengths, the system becomes orthorhombic.
Any mineral which has three axes, two of them equal in length and one unequal and all the three axis are at 90° to each other.
Typically, the crystals are shaped like four-sided prisms and pyramids. Each crystal has three axes, all perpendicular to one another. Two axes are the same length and lie on a horizontal plane. The third axis is not the same length and is at a right angle to the other two. Example: zircon
(te-trag´-o-nal) One of the six crystal systems characterized by three mutually perpendicular axes, the vertical one of which is a fourfold rotation or symmetry axis; it is longer or shorter that the two horizontal axes, which are of equal length.
