Diamond design al gilbertson free download

Step cuts usually have keels. Step-cut facets are four-sided, with the upper and lower edges being nearly parallel. For crown facets, the upper edge is parallel or nearly so to the table edge and the bottom edge is parallel or nearly so to the girdle.

Sometimes these can be five-sided like the corners on the crown of the emerald cut; see Fig. Mixed cut means that the cutter used both brilliant and step-cut styles in the facet arrangement. Ovals and cushions are often cut with step-cut pavilions, but brilliant style crowns see Fig. This breaks up the light into yet a different pattern. Remember that uniformity of color is important for the value of a colored gem. Mixing the styles of cutting will also assist in evening out the color and minimizes the effect of a small window at the culet.

For more uncommon cuts such as the Barion cut see Fig. The rose cut features a flat bottom with a dome-shaped crown reaching an apex see Fig. Rose cuts, so named because they resemble the shape of a rose bud, were originally cut in diamond in the s.

By the s this cutting style had moved over to a few colored gems such as marcasite and garnet. Recently, it has found fashion in a number of other colored gems.

The non-faceted styles of gem cutting predate faceted styles, with the earliest form being either the bead or cabochon or cab. A gemstone bead is fashioned in a variety of shapes and sizes, and is pierced for threading or stringing. The material can be transparent to opaque. The simple cab has a rounded top and flat bottom see Fig.

The usual traditional shape for cutting cabs has been an ellipse oval. This is probably because the eye is less sensitive to small asymmetries in an ellipse, as opposed to a uniformly round shape, such as a circle. The elliptical shape, combined with the dome, is also attractive.

More recently many shapes, including freeform, are used for cabs. In the case of asteriated gems such as star rubies, and chatoyant gems such as cat's-eye chrysoberyl or tourmaline, a high domed oval or round cab cut is necessary to show the star or eye, which would not be visible in a faceted cut. The back should be unpolished see the first two gems of Fig. For finer translucent and transparent gems with an eye or star that is not quite sharp, sometimes a coarser finish on the back will sharpen the line.

Any outline can be cut in any of these cabochon variations see Fig. Early forms of cabs were sometimes carved seals, scarabs, cameos, etc. Hollow gems can have one of two purposes: 1 They are used to deceive by putting colored glue behind a thin translucent wall of the gem to intensify a certain color; or 2 Exceptionally dark gems can have their apparent color lightened.

Cameos and intaglios are the most common form of carved cabs today. Cameos are made by cutting away material; the design remains above the level of the base. With intaglios, the reverse of the cameo, a design is cut into the gem below the highest part of the surface. The most common subject matters were historic or religious figures, and frequently used materials have different colored layers like banded agate which can be revealed in forming or embellishing the image the face will be one color, while the background is another color.

Shell and agate are two of the most commonly used materials, but others include amber, coral, jet, and lava. Carved gems can take any form, from freeform and geometric to carved flowers, animals, or mythical beasts and more recently modern carved gems can replicate a photo of a family member. In recent decades, the hand-carving of these types of gems has been modernized by ultrasonic machines. Gems with higher levels of intricacy cut by ultrasonic methods are not as valuable as those cut by hand.

While most commonly seen in cabochon form, composite gemstones are also found with faceted gems when two or more gem materials are bonded to form a single gem. Common forms include opal doublets two parts and triplets three parts. Sometimes faceted gems are cemented together with the intention to deceive; a natural gem material is used on the crown and glass or some synthetic is used on the pavilion.

A colored cement layer can even change the apparent color. Intarsia is a composite art form of inlaying that fits pieces of gems together to form a picture or mosaic.

Certain shapes are in higher demand and make the gem more saleable. The outline of a gem can be a variety of shapes and with each there is an almost unlimited variety of facet arrangements.

Figure shows some of the most common shapes used in the trade, each with more than one facet arrangement. A few of these names can be confusing. Emerald can refer to the outline, or to a specific facet arrangement or cutting style with that outline.

For instance, a radiant has a brilliant cutting style with an emerald outline. The square emerald a debated moniker is the same as an octagon. A triangle, trillion, and trilliant can have flat sides sometimes with cut corners , or curved sides. Other outline shape names not shown include briolette, hexagonal, keystone, kite, lozenge, pentagon, rhomboid, s-curve, seven-sided, shield, and trapezoid.

However, the overall quality of the cutting can also be grouped into broad categories and described. Note that naming these following quality types is more for convenience and is arbitrarily chosen by the author.

There are exceptions as types blend into each other and they are not always easy to classify. There are very few native-cut gems in the market today. Native-cut gems are usually cut with jamb-peg machines see Fig. Ideal Scope. Hearts and Arrows. Sarine Report. Whiteflash Diamond Imaging. Social Responsibility. ISO Certified.

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Valoria wedding rings Danhov wedding rings. Benchmark wedding rings. In addition, we offer Whiteflash original designs and custom designed jewelry created in our state-of-the-art workshop. Simon G Jewelry Tacori Jewelry. By Bryan Boyne g. Al Gilbertson G. In the process he reveals surprising facts about the role American gemologists and diamond cutters played in the evolution of diamond cutting worldwide.

American Cut - The First Years. Henry Dutton Morse opened the first American diamond cutting factory in Boston in and was intent on producing the most beautiful diamonds possible.

He had to counter the full momentum of a philosophy brought over by Dutch cutters that was focused almost entirely on retaining maximum weight from the rough. Innovations that Morse and his brilliant foreman Charles Field contributed to the industry improved diamond cutting all over the world.

In a tireless quest for constant improvement, Morse carefully studied proportions and angles and availed himself to the latest scientific knowledge of refraction in diamonds. His influence in the gemological world in the early to mid 20th century was enormous. An interesting point that Gilbertson makes is that because of events leading up to World War I, there was little direct contact between cutters in Europe and cutters in America. It is probable that Tolkowsky was not aware of the advances that Morse and other Americans had made at the time he published his work.

Robert Shipley. Eventually, Robert Shipley, a successful American jeweler, would take a deep interest in diamond cut quality. The story of how that came about is fascinating, but I will leave it for the reader to discover. Any uneven distribution of color within a gemstone is called color zoning.

Face-up color zoning has a value curve see Fig. Since uniformity of color is a mark of most fine gems, an increase in face-up color zoning is usually regarded negatively. To better observe color zoning, turn the gem upside down on a white piece of paper and look for uneven coloration.

Now turn it face-up. Can you see the same color zones or splotches of darker or lighter color that you saw when the gem was upside down?

Placing the stone in a clear jar with water or vegetable oil or baby oil—do not use oil with amber , set on a white background can help you see color zoning in a gem. For many colored gems, the country of origin, or the mining location, greatly affects the value see Fig.

For example, this is truer and more extreme for an untreated sapphire of intense blue color from Kashmir, which is worth far more than a similar sapphire mined elsewhere.

A few of the major grading labs have the equipment and expertise to determine geographic origin. Be cautious and read the report from a lab thoroughly. A standard report usually identifies the gem material, but not the geographic origin. Only if the gem was sent in for a country of origin report, will it indicate the country, such as Brazil. In that case the price will be impacted by the Brazil origin. However, that does not mean GIA will be able to determine a country of origin in every instance.

GIA determines geographic origin by collecting chemistry and spectroscopic data, and identifying types of inclusions on the sample of unknown origin. That data set is compared to sets of data from reference gems of known origins, looking for compelling evidence that indicates that the unknown is from a certain location.

In the high-end gem market, trade names have been used to denote particular gemstone colors or face-up appearances from specific geographic locations.

The names persist even when significant locations come and go. This is why a country of origin report from a major lab becomes important, indicating that the gemstone has been tested and has the features associated with that specific country.

Size, which includes the weight and face-up diameter of each type of gem material, is also directly related to value see Fig. As the size increases to that of high demand, the price per carat goes up. Some gems are rarely seen above a couple of carats e. Once gems get beyond a size that is common for jewelry, the number of interested buyers decreases significantly, and the relative value per carat diminishes.

Sometimes the saturated colors only appear in larger sizes e. Conversely, if a deeply saturated rough is cut into a larger gem, it can be too dark and not as valuable. A uniformly colored piece of rough yields gems of different color intensity as the sizes and proportions vary. For example, a gem cut from light colored rough is considered attractive if it reaches a certain size to produce enough color saturation.

In this case, a cutter might cut one large, deep gem rather than several lightly colored, well-cut gems. A piece of rough is placed on white paper, and viewed under incandescent and then fluorescent light, each time staying away from any bright sources of light see Fig. The color seen through the rough is from light that is reflected from the white paper underneath.

By using both light sources you see the colors the gem will have under both types of lighting. If the rough is too dark to see much color, it should be cut into smaller gems to optimize the color. Obviously, one could use a very bright light source to see through rough that would be black in many other situations. Wayne Emery suggests using a standard watt incandescent bulb, one foot above a white paper in a dimly lit room. Clarity is an important value factor because gems are cut to sparkle and show off their color in interesting ways.

If there are flaws that interrupt that sparkle, the gem is less interesting. Hence there is a value curve related to clarity that is also true for each type of gem see Fig. Some gem materials are almost always found with inclusions, while others are commonly eye-clean inclusions cannot be seen without magnification.