Faceting


Also found in: Dictionary, Wikipedia.

Faceting

 

(1) The industrial process of grinding and polishing natural and synthetic minerals. Grinding accomplishes removal of the bulk of the mineral by producing facets on the surface of the roughly cut mineral to impart to it the shape of the future article. Polishing is used to produce a mirror finish.

Faceting of jewelry produces an aesthetically appealing form and luster that are characteristic of each mineral, and natural flaws (inclusions, cracks, and cavities) are completely or partially eliminated. Faceting is based on calculations of the angles of inclination of the facets that provide the most effective use of the optical properties of the minerals (index of refraction and the phenomenon of total internal reflection). The ideal faceting of diamond in the circular brilliant form is the best method for revealing the natural beauty of the crystal, and it provides the maximum light effect. The main elements of faceting in a round, 57-facet brilliant-cut diamond are shown in Figure 1. Because of the high cost of the initial material, maximum preservation of the mass of minerals is of great importance in the production of jewelry. For example, nonrecoverable losses in the production of cut diamonds are 2–6 percent during cutting, 16–25 percent during facing, and 40–45 percent during faceting; total losses are 55–70 percent. Faceting of natural and synthetic gems provides great potential for making use of the mineral’s color and for varying the forms of faceted articles. Faceting of colored, opaque commercial stones (turquoise, quartzites, jasper, malachite, and so on) emphasizes the beauty of the surface pattern and imparts very simple shapes to pieces of stone (cabochon, pendant, rosette, and so on).

Figure 1. Main elements of full faceting of a brilliant-cut diamond: (1) table (an octagonal upper facet intended to capture the main light flux incident on the diamond); (2) main facets, which receive rays incident at oblique angles and transmit the light flux reflected from the base facets; (3) star facets, which multiply the number of reflections from the crown of the diamond; (4) corner facets, which receive rays incident at oblique angles through the principal facets of the crown; (5) girdle (a belt that separates the diamond into crown and base); (6) main facets of the base, which reflect the light flux, thus generating the effect of “scintillation” of the brilliant-cut diamond; (7) facets of the base

Natural and synthetic minerals of great hardness are used for industrial purposes in tools (such as cutters, drills, draw plates, spinnerets, parts for precision instruments, and glass cutters). During faceting, the crystal is oriented in such a way that the working surface of the tool corresponds to the direction of maximum hardness of the crystal (usually diamond). The cutting force of the tool should not coincide with the cleavage planes of the crystal.

(2) Combinations of facets of various shapes and sizes produced on the surface of a stone are also called faceting.

REFERENCES

Andreev, V. N. Ogranka samotsvetov, parts 1–2. Moscow, 1957–58.
Kiseleva, P. N. Tekhnicheskie almazy. Moscow, 1964.
Epifanov, V. I., A. la. Pesina, and L. V. Zykov. Tekhnologiia obrabotki almazov v brillianty. Moscow, 1971.

A. IA. PESINA