While carat weight is 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 are lighter in weight and easier to chip.

Crown height

The crown of a gemstone refers to its upper area and position 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.