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Encyclopedia > Facet

Facets are flat faces on geometric shapes. The organization of naturally occurring facets was key to early developments in crystallography, since they reflect the underlying symmetry of the crystal structure. Gemstones commonly have facets cut into them in order to improve their appearance. Crystallography (from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and graphein = write) is the experimental science of determining the arrangement of atoms in solids. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... A gemstone is a mineral, rock (as in lapis lazuli) or petrified material that when cut or faceted and polished is collectible or can be used in jewellery. ...


Of the many hundreds of facet arrangements that have been used, the most famous is probably the round brilliant cut, used for diamond and many colored gemstones. This arrangement of 57 facets was calculated by Marcel Tolkowsky in 1919. It slight improvements have been made since then, including the addition of a 58th facet (a culet) on the bottom of the stone. Since this is calculated to show maximum brilliance, round diamonds are rarely cut in any other arrangement, although recently the Princess cut is becoming popular. Other cuts, including "rose" cuts, are most typically found in antique jewelry. See diamond cuts for a in-depth discussion and diagrams of various shapes and ways of cutting faceted stones. A scattering of brilliant cut diamonds shows off the many reflecting facets. ... A scattering of round-brilliant cut diamonds shows off the many reflecting facets. ... Marcel Tolkowsky (1899-1991) was a member of a Belgian family of diamond cutters and an engineer by education. ... 1919 (MCMXIX) was a common year starting on Wednesday (see link for calendar). ... This article addresses the many styles of diamond cut. ...


Cutting facets

The art of cutting a gem with facets is a very precise activity. The aim with a facetted cut is to produce an article that sparkles with internally reflected light, and that shows off the "fire" of the stone. Accordinally, normally only transparent or translucent stones are faceted.


The angles between each facet are precisely calculated. As the aim is to maximise the effect of the internal reflections, these angles depend on the refractive index of the material. This means that although the name and general shape of a particular cut may be the same between different materials, the actual angles will be slightly different, for the maximum effect. The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ...


Thus, although cubic zirconia and rock crystal may look similar to diamond, and all can be cut in a round brilliant cut, the angles must be different to produce the same optical effects. Additionally, as diamond has a refractive index significantly higher than the other natural transparent stones, it can have a much greater sparkle than other materials. A round brilliant-cut cubic zirconia Cubic Zirconia (or CZ) is zirconium oxide (ZrO2), a mineral that is extremely rare in nature but is widely synthesized for use as a diamond simulant. ... Quartz is the most abundant mineral in the Earths continental crust. ... A scattering of round-brilliant cut diamonds shows off the many reflecting facets. ... See also: List of optical topics Optics (appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. ...


While some facets can be cut by cleavage, specialised machines are used for cutting arbitrary facets. These consist of two main features: Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ...

  • a flat abrasive, usually diamond dust of precise size bonded onto a metal disk (called 'laps') or carried by an oily fluid on a smooth metal or ceramic disk, and
  • a system for holding a stone onto the disk at a precise angle and position.

This usually requires the stone to be attached to a holder, which is then placed in an indexed vice. This allows progressively finer abrasives to be used without disrupting the orientation of the stone. The final abrasive must be smaller than the wavelength of light, so that the scratches it creates are invisible. Modern machines tend to have indexed gears for moving the stone, so that rotating the stone to cut the next facet can be more precisely controlled. An abrasive is usually a material that is used to smooth or to machine another softer material through extensive rubbing. ... The wavelength is the distance between repeating units of a wave pattern. ...


Much less commonly, faceters use cylindrical machines, which leave concave facets. This technique is most noticeably used around the gem's girdle.


  Results from FactBites:
 
Facet - Wikipedia, the free encyclopedia (532 words)
The organization of naturally occurring facets was key to early developments in crystallography, since they reflect the underlying symmetry of the crystal structure.
Of the many hundreds of facet arrangements that have been used, the most famous is probably the round brilliant cut, used for diamond and many colored gemstones.
This arrangement of 57 facets was calculated by Marcel Tolkowsky in 1919.
facet - definition of facet in Encyclopedia (395 words)
Gemstones commonly have facets cut into them as a way to improve their appearance.
Of the many hundreds of facet arrangements that have been used, the most famous is probably the round brilliant cut, used for diamond.
The aim with a facetted cut is to produce an article that sparkles with internally reflected light, and that shows of the fire of the stone.
  More results at FactBites »

 
 

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