Understanding How Gemstones are Weighed and Measured

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.

Posting by Sefa di 01:06