The difference between the facet gemstone and cabochon gemstone:-
Facet and cabochon are the types of cutting styles of gemstones. If you look at the sample free streaming videos of facet (video no. 1) and cabochon cutting styles (video no. 2), you will understand.
FACETS The following information is from the website:- http://en.wikipedia.org/wiki/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 by allowing them to reflect light.
Of the 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 first early version of what would become the modern Brilliant Cut is said to have been devised by an Italian named Peruzzi, sometime in the late 17th century.[1][2] Later on, the first angles for an "ideal" cut diamond were calculated by Marcel Tolkowsky in 1919. Slight modifications have been made since then, but angles for "ideal" cut diamonds are still similar to Tolkowsky's formula. Round brilliants cut before the advent of "ideal" angles are often referred to as "Early round brilliant cut" or "Old European brilliant cut" and are considered poorly cut by today's standards, though there is still interest in them from collectors. Other historic diamond cuts include the "Old Mine Cut" which is similar to early versions of the round brilliant, but has a rectangular outline, and the "rose" cut which is a simple cut consisting of a flat, polished back, and varying numbers of angled facets on the crown, producing a faceted dome. Sometimes a 58th facet, called a culet is cut on the bottom of the stone to help prevent chipping of the pavilion point. Earlier brilliant cuts often have very large culets, while modern brilliant cut diamonds generally lack the culet facet, or it may be present in minute size. The Princess cut is also a popular diamond cut. See diamond cuts for an in-depth discussion and diagrams of various shapes and ways of cutting faceted stones.
The Sample of facet gemstone:- (There are many types of facet cuttings.) The following free streaming video is from the website:- (video no. 1)
CABOCHON The following information is from the website:- http://en.wikipedia.org/wiki/Cabochon
A cabochon or cabachon, from the Middle French caboche (head), is a gemstone which has been shaped and polished as opposed to faceted. The resulting form is usually a convex top with a flat bottom. Cutting en cabochon is usually applied to opaque gems, while facetting is usually applied to transparent stones. Hardness is also taken into account as softer gemstones with a hardness lower than 7 on the Mohs hardness scale are easily scratched, mainly by silicon dioxide in dust and grit. This would quickly make translucent gems unattractive—instead they are polished as cabochons, making the scratches less evident.
In the case of asteriated stones such as star sapphires and chatoyant stones such as cat's eye chrysoberyl, a domed cabochon cut is used to show the star or eye, which would not be visible in a facetted cut.
The usual shape for cutting cabochons is an ellipse. This is because the eye is less sensitive to small asymmetries in an ellipse, as opposed to a uniformly round shape, such as a circle, and because the elliptical shape, combined with the dome, is attractive.[why?] An exception is cabochons on some watches' crowns, which are round.
A round sapphire cabochon on the crown of a men's dress watch. Amber pendants. The oval cabochon pendant is 52 by 32 mm (2 by 1.3 inches). The procedure is to cut a slab of the rough rock, then to stencil a shape from a template. The slab is then trimmed to near the marked line using a diamond blade saw—called a trim saw—and sometimes followed by "nibbling" to the line. The purpose of nibbling is to speed the shaping of the material when using silicon carbide grinding wheels. Most lapidary workshops and production facilities have moved away from silicon carbide to diamond grinding wheels or flat lap disks.
Once the piece is trimmed and nibbled, it is usually mounted on a handle to assist manipulation. This procedure is called "dopping"; it is normally done by adhering the stone with hard wax onto a length of wooden dowel called a "dop stick". The piece is then ground to the template line, the back edges may be bevelled, and finally the top is sanded and polished to a uniform dome.
The sample of cabochon gemstone. The following free streaming video is from www.youtube.com (video no. 2)
The following video is the cat's eye gemstone: the word 'cat's eye' in the gemstone business is the white line in the middle of the stone which you can see from the following free streaming video from www.youtube.com Cat's eye is natural. When the gem cutter sees that the rough gemstone has the natural cat's eye, he will cut cabochons only in order to be able to see the cat's eye. Facet cutting cannot present the natural cat's eye. The cat's eye must be in the middle of the stone. In the past it's rather difficult for the cutters to cut them in the middle of the stones, but it's not difficult now as there are the smart cutting machines to do this kind of work.
The following is the star gemstone. The word 'star' in the gemstone business is the six white lines on the top of the stone. 'Star' is natural. When the rough gemstone has the star, the cutter will cut it in cabochon only to be able to see the star. He must cut the gemstone with the star in the middle of the stone, otherwise the price will be dropped. The following free streaming video is from www.youtube.com