Understanding Gemstones
The beauty, rarity and historical mystique of gems are timeless. Their richly diverse varieties and colors come in a kaleidoscopic array that puts Diamonds to shame. However, before you make a purchase, you will need a basic understanding of gems.
Understanding the value of gems is essential to making a successful and rewarding purchase. Regardless of the gem variety you’re buying, there are a few constant rules to bear in mind.
Color
Color is the single most important factor when evaluating colored gems. Basically, the more attractive the color, the higher the value. Bright, rich and intense colors are valued over those that are dark or light. Although specific colors hues can affect the prices of gems, personal preferences are also very important. The colors seen should ideally remain attractive regardless of prevailing light conditions. Whether viewed indoors, outdoors, by day or by night, a gem should always remain beautiful.
The mixing of color hues into combinations, such as purple-blue in Tanzanite and bright blue-green in Apatite is attractive and value enhancing. Many gems also have specific expressions to denote the very top colors found within a species. For example, Cornflower Blue used for Sapphire. Such terms are equable with the most desirable colors to be found within a gem species (i.e. colors that cannot be bettered).
Optical Effects
Some gems exhibit unusual optical effects known as phenomena. These rare and beautiful effects very often add value to gems. The Cat’s Eye Effect, the Star Effect and the Color Change Effect are very popular phenomena and are highly valued.
Chatoyancy
Asterism
Color Change
Iridescence
Aventurescence
Chatoyancy: Chatoyancy or the Cat’s Eye Effect is a reflection effect that appears as a single bright band of light across the surface of a gemstone. This phenomenon is commonly found in Chrysoberyl, Tourmaline and Tigers Eye.
Asterism: Asterism or the Star Effect is a reflection effect that appears as two or more intersecting bands of light across the surface of a gem. This phenomenon is commonly found in Ruby, Sapphire and Garnet.
Color Change: Color change gems are those that distinctly change their color when viewed under two different light sources. This phenomenon is commonly found in Alexandrite, Sapphire and Color Change Garnet.
Iridescence: Iridescence is the rainbow like color effects seen in some gems. This phenomenon is commonly found in Opal, Ammonite and Moonstone.
Aventurescence: Aventurescent gems are those that have a colorful play of glittering reflections from small metallic inclusions. This phenomenon is commonly found in Sunstone, Aventurine Quartz and Gold Stone.
Cut & Polish
Unlike Diamonds, colored gems possess variable optical properties and are not cut to a uniform ideal. A well-cut colored gem exhibits even color, an acceptable number of inclusions, good brilliance and shows the majority of Carat weight when viewed from the top.
Table
Girdle
Crown
Pavillion
Culet
(may or may not be faceted)
Industry Standard Anatomic Layout Of A Faceted Gemstone
Broadly, the styles of gem cutting can be divided into Faceted Gems (gems with geometrically shaped flat polished faces) and Non-Faceted Gems (those Gems that do not have geometrically shaped flat polished faces such as cabochons).
Antique Cushion
Baguette
Emerald Cut
Briolette
Heart Cut
Octagon Cut
Pear Cut Common Cuts
Marquise Cut
Round Brilliant Cut
Oval Cut
Square Cut
Trilliant Cut
Round Cabochon
Princess Cut
Carat Weight
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 Grammes. 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, other than the fact that they both originate from the use of carob seeds, which in this case was used to weight the alloys added to gold.
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.
Rarity
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 an “exotic 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.
Historical Connotations & Origin
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 and also more ethical.
When specifying the origin of the gemstones we sell, Gems TV undertakes a series of checks based on our experience to ensure that each gemstone displays the characteristics indicative of the origin specified. While Gems TV does everything possible to ensure that the origins we specify are correct, others may disagree with our assessment. Please be aware that determining origin is not always absolute and as with many aspects of gemology, is subject to the experience and opinion of the gemologist performing the assessment.
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.
