JEWELRY TIPS: April 2009

Although bigger seems better and more expensive, it's not always so in the world of jewelry. In fact, size isn't even synonymous with carat weight and you need to keep that in mind when shopping for gemstones.

Carat Weight versus Size
Diamonds and colored gemstones alike are evaluated and appraised according to the 4C’s which are made up by cut, color, clarity, and carat weight. Carat weight is very much different from size and definitely more important than the latter. Also, take note that carat is different from karat, which is the measurement unit used for gold. Carat weight uses the abbreviation ct and ct TW for carat total weight.

In the past, carob seeds were traditionally used to measure a gemstones weight because of its uniform shape and size. In 1913, however, the jewelry industry managed to set universal standards for measurement and the carat weight system was born.

Now, one carat is always equivalent to one-fifth or twenty percent of one gram. One carat is made up of one hundred points. As a gemstones weight goes up, so does its value or price per carat.

The way carat weight is discussed is occasionally a cause for confusion. Remember that a gemstone with .005 ct may be called a half point gemstone. A .25 ct gemstone could be called a quarter carat while a .50 carat gemstone may be referred to as a half carat or fifty points.

Gemstones are often listed according to their size because it is more uniform than carat weight. Two different gemstones may have the same size but different carat weights and consequently, different prices as well.

Factors Affecting Gemstone Carat Weight

Gemstone Material A 1 carat ruby is smaller than a 1 carat emerald. This is mainly due to the gemstones specific gravity. A gemstones denseness level can make it carry greater weight even though it has a smaller size than other gemstones with the same carat weight. While carat weight is very much important for traditional and much-prized gemstones, it tends to lose its significance when it comes to common gemstones with high supplies like blue topaz, citrine, and amethyst. Amethyst, in fact, used to be classified as one of the precious stones but its price went down when loads of shipment arrived from Brazil in the 19th century.

Gem Shape or Cut The shape and cut can occasionally affect the carat weight. While most jewelry designers cut gemstones with size and carat weight in mind, others place more importance on its aesthetic value and may therefore reduce carat weight and size in favor of improved looks. The same can be said for shape as well.

Table Diameter The table diameter is often considered important only for measuring or evaluating the brilliance of a given gemstone, but what few people realize is that it can affect the gemstones carat weight as well.

Similar to gem cut and shape, if the table diameter is shaped in such a way to maximize its window-like characteristics, carat weight might be consequently sacrificed.

Today, studies show that a lot of gemstones sold on the market are cut to take commercial concerns into consideration. Many of these gemstones report loss in weight of just 10% or lower. Some are even cut to the extent of making them appear bigger as well.

Girdle Thickness The girdle is the dividing line between a gemstones pavilion and crown or its bottom and top facets. Ideally speaking, girdles must be extremely thin and preferably visible only to the naked eye like a light line. Thick girdles not only reduce brilliance and light yield but negatively affect the gemstones color as well. Girdles are often referred to as edges and they are graded as any of the following: very thin, thin, medium, thick, thick, and very thick. Thin girdles look better, but they're lighter in weight and easier to chip.

Crown Height The crown of a gemstone refers to its upper area and positioned on top of the girdle. Acceptable crown height for gemstones is between 11.0 to 16.2% of the girdle diameter. Greater crown height often means greater carat weight.
Pavilion Bulge The pavilion is the bottom portion of a faceted gemstone. Greater bulge usually means heavier carat weight.
Culet Size This is the facet at a gemstones tip. Like the girdle, culets are better invisible to the naked eye. It may be sharp or pointed.

read more...... “Understanding How Gemstones are Weighed and Measured” »»

It is easy to feel intimidated and out-of-place when you're visiting a high-class jewelry shop for the first time. To avoid making unwanted and uniformed purchases, improve your knowledge about jewelry starting with the tips below. If you speak the same language people in the jewelry industry speak then you'll surely go home with the jewelry piece you want, need, and definitely can afford.

The Meaning of Gemstone

A gemstone may be a rock, mineral, or even a petrified material that's cut and polished to be used for making jewelry pieces. It may be even harvested like pearls or organic like amber, just as long as it has aesthetic appeal. In the old days, precious gemstones only referred to the Big Three: emeralds, sapphires, and rubies. Everything else was labeled as semi-precious gemstones.

Categories today, however, have been thankfully changed and widened to avoid further confusion.

The Ins and Outs of Lapidary

Lapidary refers to the process of cutting and polishing gemstones. Rough materials are left uncut and unpolished. Cobbed materials are referred to as fractured. Materials like silicon carbide and diamond, due to their hardness, are used for cutting gemstones in a progressive abrasion process. Compounds like aluminum and chromium oxide are, on the other hand, used for polishing gemstones.

Common cutting techniques include tumbling, drilling, polishing, lapping, sanding, grinding, and sawing. Cut gemstones are then polished into several forms such as sculptures, intaglios, cameos, mosaics, intarsias, inlays, spheres, beads, cabochons, and faceted stones.

Sawing The main tool used in sawing is a copper or steel blade with diamond grit on the edges. Water or oil is used to eliminate cutting debris and prevent the blade and stone from overheating.

Grinding Diamond-impregnated grinding wheels made of silicon carbide are used to grind gemstones and shape them into a pre-form. Liquid substance is also used to prevent both the stone and tool from overheating.

Sanding This process is similar to grinding but utilizes finer abrasives instead. It is often performed as a follow-up after grinding for removing scratches caused by the previous cutting technique. For round gemstones, a belt sander may be used in accompaniment to ensure smoother and rounder curves.

Lapping A lap, which is a flat disk that's either vibrating or rotating, is used to create flat surfaces rather than round ones. The process however is similar to sanding and grinding.

Drilling This technique is used if the lapidarist wishes to create a hole through or in a gemstone. Drilling tools may be rotating or ultrasonic.

Tumbling A gemstone that's placed in a rotating barrel filled with water and abrasives is tumbled for polishing. These gemstones are usually roughly shaped and the polishing process is gradual and performed with interval washings. Sometimes, vibratory machines are used in lieu of rotating barrels. This time, the barrels vibrate rather than rotate. Tumbling techniques are also used to polish metal jewelry pieces.

Cabochons Cabbing or cabochon cutting is achieved by gluing or dopping the gemstone into a metal or wooden dopstick or simply holding it in place. The cabbing machine then twirls and creates a round smooth surface top and a flat or slightly rounded bottom for the gemstone. This is usually an alternative to faceting for gemstones that possess too many inclusions.

Faceted Stones Gemstones that have faceted forms reflect brilliant color and clarity from all sides and at all light levels. This technique is most suitable for transparent stones. Today, new techniques like grooves and concave facets are used to create new looks for faceted gemstones.

The Importance of Cut and Polish in Gemstones

Cut is one of the all-important 4C's and which is used not only to appraise diamonds but gemstones in general as well. Gemstones are often cut with regard to their size alone. But beautifully cut gemstones take their color into consideration as well.

If you are shopping for faceted gemstones, one way of determining the excellence of its cut is to check if its able to reflect light on a consistent level throughout its surface. Look for symmetrical rather than asymmetrical cuts as well. Lastly, be reminded that cut is different from shape.

Polish is simply like adding the final touches to a gemstone. A well-polished gemstone is one with evenly smooth gloss and with no visible scratches on its surface.