DDG Ass #17 Key Terms & Concepts PDF

DDG Ass #17 Key Terms and Concepts Annealing—A controlled heating and cooling process. Graphitization—Formation of graphite around a diamond’s mineral inclusions and feathers that results from the extreme conditions of HPHT treatment. Internal Laser Drilling—A clarity treatment that uses a...

DDG Ass #17 Key Terms and Concepts Annealing—A controlled heating and cooling process. Graphitization—Formation of graphite around a diamond’s mineral inclusions and feathers that results from the extreme conditions of HPHT treatment. Internal Laser Drilling—A clarity treatment that uses a laser focused on or near an inclusion to enlarge existing cleavages or create new ones, providing a path for a bleaching solution to dissolve the inclusion. Interstitial Positions—Spaces in the regular framework of atoms that are usually uninhabited. Irradiation—Exposure of a material to radiation. Laser Drilling—The use of a laser beam to reach a diamond’s dark inclusions and disguise or eliminate them. Key Concepts: Laser drilling can make a diamond more marketable by improving its appearance. Major gem labs report features left by laser drilling as clarity characteristics because they are permanent. Fracture filling makes a diamond’s fractures and cleavages less visible by using a high-RI glass filler. Some signs of fracture filling are the flash effect, trapped gas bubbles, flow structure, and a crackled texture. Disclosure of fracture filling is an industry requirement. Irradiated diamond color can change if the diamond is exposed to heat during repairs, recutting, or repolishing. The color resulting from irradiation can vary based on the defects already present in the diamond. Irradiation of a type I diamond creates a blue to green bodycolor depending on the starting material. Annealing a diamond after irradiation results in the reorganization of color centers to further change the bodycolor of the diamond. Irradiation and subsequent annealing of a type Ia diamond creates a yellow, orangy yellow, yellow- green, or brown bodycolor. Irradiation and annealing of a type Ib diamond creates a pink bodycolor. Gemological laboratories have the advanced equipment to determine color origin. HPHT color treatment of diamonds uses the same equipment as HPHT diamond growth, but at slightly different pressures and temperatures. The HPHT treatment process works by rearranging defects in a diamond’s crystal lattice. All diamonds need repolishing after HPHT treatment because of the high temperatures and pressures. HPHT processing of type Ia diamonds can enhance color by rearranging vacancies and nitrogen atoms within the crystal lattice. HPHT treatment of type II diamonds can enhance color by removing vacancy clusters that cause a brown or gray bodycolor. Some treaters use a combination of treatments to achieve the desired bodycolor. Coatings were one of the earliest methods of diamond color modification. Modern silica coatings are fairly durable but not permanent.