Gemstone guide

CARAT WEIGHT

The term carat comes from the carob bean that was used to weight gemstones, being its weight approximately one carat. The carob bean was also used in the gold trade and the word karat is now used to indicate its purity (see our metal guide).

In 1907 the fourth General Conference on Weights and Measures adopted the metric carat as a unit of mass for gemstones and it equals 1/5 of a gram or 200mg. In 1913 was introduced in the USA and in 1914 in the UK.

Usually weight less than a carat are referred to as points. For example, 0.50 ct is 50 points.

Since the carat is a weight, there isn’t an equivalent exact size in mm, for example two stones can have the same top measurements but different height giving a different weight. A 0.50ct round diamond is approximately 5-5.1mm, a 1ct round diamond is 6.3-6.5mm and a 2ct round diamond is 8-8.2mm

Gemstone SHAPES

The shape of a gem is its face-up outline. Gemstones can have any shape, in fact they can be cut in the shape of an animal, tree or any shape you like. The most common shapes, though, are the following:

Cutting Style

The cutting style is the way a gemstone is cut. Before the 14th century they were usually cut in beads or cabochons, which have a dome-shaped top. Only after the 1450 diamonds started to be faceted, since they look dull in a cabochon cut and facets create brilliance and sparkle in a gem.