Crystal, dodecahedron, octahedron, maccle … This is how we’ve been describing some of the new stones on our site lately. If you’re not a gemologist, it probably hasn’t meant much to you, so we asked our in-house GIA certified gemologist Rachel Kaminetsky to give an overview of the different shapes of diamonds, and how particular physical characteristics are described.
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First of all, all crystals are classified according to the internal structure and arrangement of the atoms that compose them. Diamond belongs to the cubic crystal system, which is the most symmetrical of crystal systems. The basic crystal shape, or habit, of diamond is the octahedron; a form with eight equal triangular sides, looking like two pyramids connected at the base.
Octohedrons from the Mir Mine in Russia.
Other shapes of diamonds are the cube (6 equal square sides, or faces) and the dodecahedron (12 equal “diamond” or rhombus-shaped sides).
Dodecahedron sourced from Canada.
Rough diamonds are found in a wide range of shapes and appearances, although their internal arrangement remains orderly and symmetrical. However, during formation, conditions surrounding the diamond may change, causing a shift in direction of the stacking atoms, and resulting in some unique features.
Parallel grooves, trigons, which are triangular depressions, or cubic faces, which are square or rectangular depressions are all examples of growth marks.
Diamond crystal displaying trigons on its surface.
Twinned crystals, such as maccles (the flat, triangular diamond crystals) are the result of a crystal distorted during growth. They have two opposing crystal directions, making it a challenge for diamond cutters, who are “dictated” how a diamond may be cut by the internal structure of the gem. However, for designers who prefer using rough, all these characteristics may pose a beautiful and unique feature in a one of a kind creation.
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