Concave Faceting
Concave gem faceting cuts are a relatively new trend on the gem-cutting scene (amethyst - above, left). Invented by Doug Hoffman in the early 1990s, the technique was perfected by American gem-cutter Richard Homer.
Concave Cut Traditional gem facets are flat or two-dimensional. Concave cutting creates facets that are curved or three-dimensional. These curved facets refract more of the ambient light and return it to the eye as brilliance.
concave
Hollow and curved, like the inside of a hollow ball.
convex ...
Concaves/Naturals: natural indentations in the surface of a gemstone created during crystal formation. These growth marks are usually found on the girdle and do not affect the gemstone's beauty or luster.
Concave cut
The concave cut is a three dimensional conical shaped facet applied to the pavilion of the gem that creates depth as well as length and breadth. Instead of the facets being joined by an angle they are joined with a groove.
Concave: Concave simply means "curving inward", like the inside of an egg shell. The opposite of Convex.
Concave Ring
A ring that has a feature stone or feature design at the top that curves inward instead of outward.
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[Concave cut iolite freeform, round brilliant cut iolites in earrings] ...
Concave Design Bali Silver Cuff Bracelet
Price $139.99
Balicuff 06
Hand made in Bali ...
Concave is described as inwardly curved. Historically, gemstones were faceted with flat surfaces applied at various angles. However, recent advances in technology made possible the development of machinery that could produce curved surfaces on gems.
Concave: The opposite of convex it means to curve inward.
Conch: A mollusk with a pearly shell that vary in color with pink being the most prized. Conch is made into cameos and beads.
Two concave plates that form a hollow receptacle, a form used in ancient jewelry
C
Cabochon ...
Circles: Concave, concentric rings on a pearl's surface.
Clean: Absence of blemishes on a pearl's surface.
Color: An evaluation of quality used to describe the color of a pearl.
If a ring is concave, or rounded, on the inside to create a more comfortable fit for the owner the ring or shank is often referred to as being Comfort fit.
Crown:
The upper part of a gemstone, between the girdle and the table.
Bulla
Two concave plates that form a hollow receptacle, a form used in ancient jewelry
Cabochon
Stone with a smooth carved surface, domed and unfaceted with a flat base ...
Bead tip is a concave metal piece, attached to a metal loop, used to add thread to a clasp. It is used between the clasp and the beading thread to hide the beading thread knot which is covered inside the concave piece.
Bracelet Link ...
Collar - A band worn close to the neck
Concave - Curving inward, like the inner surface of a ball
Convex - Curving outward, like the outer surface of a ball ...
parabolic dune A horseshoe-shaped dune having a concave windward slope and a convex leeward slope. Parabolic dunes tend to form along sandy ocean and lake shores. They may also develop from transverse dunes through deflation.
the top, also known as 'drop-cut' Bronze An alloy of approximately 8 parts copper to 1 part tin Buff top cabochon Style of stone cutting where the top of the gemstone is a dome (en cabochon) and the pavilion is faceted Bulla Two concave ...
Spheres are initially sawed into cubes or dodecahedrons and then ground to shape between two pipes or rotating concave cutters, allowing the stone to rotate freely in any direction to form a perfect spherical shape.
Their pendants were made of hollow concave places between which was a relic, or an object held in veneration as a charm, cure or preventative of evil or danger. Pendants grew to hold great importance towards the closed of the fifteenth century.
The cubes then are shaped into round by grounding it between the rotating concave cutters. The stone revolves around the concave cutter irrespective of the direction and attains the desired spherical shape.
Cabochon cut stones usually have a flat base, but sometimes a slightly convex base is used, especially in opals and in moonstones, and some stones of very dense color are cut with a concave base to thin them and thus to reduce their color.
Circles: Concentric rings formed on the surface of a pearl that are concave in appearance. If circles are apparent on more than 1/3 of a pearl's surface then the term "circle pearl" is applied to describe the shape of a pearl.
washing is performed in a kind of pan or sieve made of thin strips of bamboo neatly plaited, and supported by a circular frame of bamboo about 1 inch deep, the diameter being between one and two feet; the bottom of this pan is very slightly concave, ...
Cuvette
A raised relief carved into a gemstone in a concave depression.
Density
Mass per unit volume. The amount of matter in a given space. The higher density/atomic mass of a gemstone, the more it weighs for a given size.
QAR141, Quartz, Rose De France Amethyst, 'A', [N], 10.1x8.2mm Emerald, Concave Cut, 2.86 ct. $ 44.99
QAR140, Quartz, Rose De France Amethyst, 'A', [N], 10.1x10.2mm Trillion, Concave Cut, 2.69 ct. $ 39.99
Amethyst (Quartz) ...
A gemstone with a smooth concave depression.
chevron
A difficult bead pattern that features layering white, red, and blue glass.
Fluted: A long, usually rounded concave grooves repeated in vertical parallel lines as a decorative motif. Commonly seen on Greek and Roman columns.
Mobe - A large one-sided cultured pearl which has formed on the concave shell of the oyster and is flat on one side.
Off Round - Any pearl that is not "round," but has a slightly irregular shape. Round - A perfectly round pearl.
Pearl Size: ...
Dapping-die: An iron cube with a variety of concave sinks on its faces, used with corresponding punches to produce cup-shaped forms in sheet metal.
In observing the lines of the table-edges - they are formed by the table-edges and in their elongation by the edges of the table facets - it can be seen that these, according to the size of the table, may be convex, straight or concave (Fig 211 and ...
A metal Finding used to hide string knots. The knot sits inside the concave piece of the tip. See also Calotte.
Above are some gold-plated metal Calottes.
BEADED BEADS ...
3rd Place
Richard P. Homer
Columbia Gem House, Inc.
38.69 ct. round concave tube-set brilliant cut mint green tourmaline.
indented natural The original skin of the rough diamond that is at least slightly concave in relationship to the surrounding polished facets. It can be considered a blemish depending on its size and location.
New in this era was that the heads of the ring (which held the inlays) had a concave shape at the base to follow the rounded shape of the finger. The shanks of these rings were small at the base and widened towards the head.
The cleavage in one of such masses appears fibrous and concave in crystals of small size. The colour is more or less dark, and does not resist fire. This gem possesses double refraction, but in a moderate degree.
 See also: Jewel, Rough, Gemstone, Cut, Shape
  
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