Gemstone weight is measured in Carats. This unit of measurement originates from the traditional use of carob seeds to weigh gems. Carob seed were used because of their consistent size and shape. One Carat is the equivalent of 0.20 Grams. Further divided into 100 smaller units known as Points, the term carats is often confused with “Karats”. “Karat” is a measurement of gold purity and has no relationship to the term Carats.
As the weight of a gem increases, so does its price per Carat. Large gems are always rarer than smaller ones, so per Carat prices rise exponentially. A 3 Carat Ruby is always worth far more than three 1 Carat Rubies of the same quality.
Gemstone prices also increase rapidly when in excess of certain key weights. For example, a 2.01 Carat Ruby has a higher price tag than a 1.99 Carat Ruby, despite a negligible difference in actual size. Pricing is said to suffer a “Non Linear Scale of Increments”.
Clarity
Most gems contain tiny natural features called inclusions. Mostly microscopic in nature, they are most easily glimpsed under magnification. Inclusions that don’t interfere with the brilliance, sparkle and fire of a gem don’t affect the value.
Many gems have tendencies to be more included than other varieties. For example, Emeralds are known to be far more included than Sapphires and this should be taken into account when making your selection.
The clarity of gems is determined by judging the amount and location of inclusions seen. Basically, the higher the clarity grade, the higher the value of the gem
Durability
Gems with better durability and resistance to wear are generally more highly prized than those of lesser durability.
Species of gems that are rich in history and lore are more highly prized by some individuals than those lacking a rich lore or history. A good example of this is Rubies from the Mogok Valley in Burma. While many people are prepared to pay considerably more for Rubies from Mogok, other individuals may feel that a comparable Ruby from Madagascar will be better value.
Pairs & Suites
Pairs or suites of gems matched for color, clarity and cut are valued more highly per Carat or per gem than single gems of the same quality. Given the rarity of many gems, a matching set is disproportionately hard to find and will command a higher per Carat price than if each of the gems from the suite were sold separately.
