Diamonds, also known as Jin Gangzuan, are called diamonds. Its chemical composition is carbon, which is the only single element in gemstones and belongs to equiaxed crystal system. The crystal structures of the seven basic patterns of (1) diamonds are very complicated, but there are mainly the following three types: (1) tetrahedron, (2) octahedron and (3) rhombic dodecahedron. Because diamond belongs to a cube, with three equal-length axes perpendicular to each other, it is the system with the highest degree of symmetry in the crystal. The cubic crystal system of diamond produces unique crystal patterns with its unique "habit". These basic patterns are as follows:1; A cube consists of six square faces, each of which is at right angles to each other and the axes are at right angles to each other. Industrial diamond crystals usually appear in the shape of cubes. 2; Octahedral, which consists of eight equilateral triangular faces, has the same crystal axis length from the center point to each face. Most gem-grade diamond crystals are of this shape. 3; A dodecahedron consists of twelve rhombic faces. It is unusual for diamond crystals to appear in this shape. 4; Tetrahedron, replaced by 24 isosceles triangles, becomes this shape. Gem-grade diamond crystals rarely have this form. 5; An equilateral quadrilateral consists of 24 faces of an equilateral quadrilateral, and eight faces of an octahedron are replaced by three equilateral polygons to form this shape. There are not many such gem-grade diamonds. 6; An octahedron consists of twenty-four isosceles triangular faces and eight octahedral faces, each of which is equal to three faces.

Replacing the angle with this shape is a common variant of octahedron. 7; A hexahedron consists of twenty-four triangles, and each face of an octahedron consists of six triangles. (2) In fact, the crystal morphology of the growth line does not appear in a simple basic form. It is usually a mixture of two or more crystals, but it is often an octahedral mixture. There is a feature on the surface of diamond crystal, which is very important for cutting workers, and that is the' growth line', which can help us identify the authenticity of diamonds. Many older diamonds can't show their unique brilliance because the cutting pattern is too old and the angle ratio is wrong, so the growth line left by the unpolished surface becomes an important reference for identification. There are certain standards for the growth line. The growth line on the octahedron becomes a triangular groove, and the three sides of the triangular groove must be parallel to the sides of the octahedron. The growth line on the rhombic dodecahedron is groove-shaped, and the groove is parallel to the diagonal of the rhombic surface. The growth line on the cube becomes a square groove, and the four sides of the square groove must be parallel to the diagonal of the cube surface. (3) In addition to the seven basic forms mentioned above, there is another very important form, namely "twin". There are many kinds of twins, but only two or three are common. The octahedral twin is called Michael by experts and is the most common twin. Cutting, sawing and polishing are very difficult because the lines of twins are inconsistent. At the same time, twins are relatively flat, and cutting into round drills is very heavy. Therefore, twin is undoubtedly a challenge for the cutter.