Is this a rough diamond?
Diamond, also known as diamond, the mineral name is diamond. Its chemical composition is carbon, which is the only one composed of a single element in gemstones and belongs to the equiaxed crystal system.
(1) Seven basic styles
The crystal structure of diamond is very complicated, but there are mainly three types: (1) tetrahedron, (2) octahedron, (3) rhombic dodecahedron. And because diamonds belong to a cube, the cube has three equal-length axes perpendicular to each other, which is the highest symmetry system among crystals. The cubic crystal system of diamonds produces unique crystal patterns with unique "habits". These basic patterns have the following seven types:
- A cube is composed 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 often appear in the crystal shape of a cube.
- An octahedron is composed of eight equilateral triangle faces. The length of the crystal axis from the center point to each face is the same. Most gem-grade diamond crystals have this shape.
- The dodecahedron is composed of twelve diamond-shaped faces. Diamond crystals appearing in this shape are not common.
- Tetrahexahedron, which is replaced by twenty-four isosceles triangles. Gem grade diamond crystals rarely have this form.
- The unequal quadrilateral is composed of twenty-four unequal quadrilateral faces. The eight faces of an octahedron are replaced by three unequal sides each to form this shape. This gem-quality diamond is also not much.
- The three-octahedron is composed of twenty-four isosceles triangle faces. The eight faces of the octahedron are replaced by three equal triangles on each face to become this shape. It is a common variant of the octahedron.
- The six-octahedron is composed of twenty-four triangles. Each face of the octahedron is composed of six triangles.
(2) Growth lines
In fact, the crystal form does not appear in a simple basic form. It is usually a mixture of two or more kinds of crystals but tends to be a mixture of octahedrons.
There is a feature on the surface of the diamond crystal that is very important to the cutter, that is, the growth pattern', which can help us identify the authenticity of the diamond. Many older diamonds are cut too old and the angle ratio is not correct so that they can not show the unique brilliance of the diamond. Therefore, the growth pattern left on the unpolished surface becomes an important reference for identification.
The growth pattern has a certain standard. The growth pattern 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 pattern on the rhombic dodecahedron is groove-like, and the groove is parallel to the diagonal of the rhombus. The growth pattern on the cube becomes a square groove, and the four sides of the square groove must be parallel to the diagonal of the cube face.
(3) Double crystal
In addition to the above seven basic forms of diamond crystals, there is also a very important shape called "double crystals". Double crystals are also very important to cutters. There are many types, but only two or three are more common. They have an octahedral surface. The double crystal, called Michael by experts, is the most common double crystal.
Because the texture of the double crystals is inconsistent, it is difficult to cut, saw, and polish. At the same time, the double crystals are relatively flat, and they have to be cut into round diamonds, and the weight loss is great. Therefore, the double crystal is undoubtedly a challenge for the cutter.