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”.
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.
Gems with better durability and resistance
to wear are generally more highly prized than those
of lesser durability.
Generally, rare gems are more highly
prized than more common varieties. However, if a gem
variety is so rare that it is essentially unknown to
the general public, it is often classified as a "collector
gem". Gems such as Boracite, Childrenite and Simpsonite
are extremely rare, attractive and durable, but they
are unlikely to command prices appropriate to their
rarity because fewer people are aware of their existence.
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 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.