Where do you begin the journey into the magical
world of color? What are the factors that make a gem rare and valuable
Much like a diamond, the various combinations
of a stone's cut, color, clarity, and carat weight, along with
availability and accessibility, determine rarity. You will find a brief
description of those features here. These explanations are based on the
system for gemstone evaluation established by the Gemological Institute
of America. For more information on GIA, please visit www.gia.org.
Color: Color is typically the most important
value-setting factor for gemstones. All gems have a preferred color or a
relatively small range of preferred colors. The more the color varies
from this range -- lighter or darker, more vivid or less -- the less
valuable the stone.
Color is composed of three dimensions: hue,
tone, and saturation.
- Hue refers to the impression of color
usually noticed immediately, such as red, yellow or blue.
- Tone refers to the degree of lightness or
darkness of an object.
- Saturation defines the degree of purity of a
Cut: Cut refers to the shape or design of a
stone, arrangement of facets, as well as the precision of the stone's
proportions and finish. the cutting process reveals the beauty of a gem.
Gemstones are cut into shapes we are familiar
with such as oval, emerald, pear, round, and marquise. in addition, they
can be carved or fashioned into almost any design imaginable.
Proportions involve the balance and appeal of the basic design. Finish
refers to the detail of the workmanship. A well-proportioned cut with a
fine finish will show a stone's optical properties to its fullest
potential. When all other factors are even (color, clarity, and carat
weight), a better-cut gem will be more valuable.
Carat Weight: The size of a gemstone is
measured, not by its dimensions, but by weight. One carat, the
traditional unit of measurement for gemstones, is equal to approximately
0.2 grams. you may also hear the weight of a gemstone referred to in
points. A point is equal to 1/100 of a carat; therefore a 75-point
gemstone equals 0.75 carat.
Two different gemstones may have the same
dimensions but different weights. This is due to the specific gravity or
density of the gem mineral. This difference can help gemologists
identify a gemstone.
Up to a certain point, the larger a stone is,
the more rare it is and the higher the price it will command. For stones
that commonly occur in larger sizes, the value may decrease if the gem
reaches a size that makes it impractical for jewelry use.
Source: Gemological Institute of America
Clarity: A gemstone's clarity grade is directly
related to its rarity. Clarity refers to a gemstone's relative freedom
from clarity characteristics. Clarity characteristics include
inclusions, which lie within the stone, or blemishes, which lie on the
surface of a gem. The fewer clarity characteristics, the more rare the
Each variety of gemstone has its own clarity
standards. For example, Tanzanite is virtually inclusion-free, while
Emerald almost always contains clarity characteristics. For this reason,
Gemological Institute of America's grading system divides transparent
colored gemstones into three clarity types. This allows gems to be more
evenly evaluated as it takes into account the individual nature of each
gemstone. Each type is further divided into five grading descriptions.
Clarity Types: Type I gems are often virtually
free of clarity characteristics. The stones most commonly seen in the
- Green Tourmaline
- Topaz - Blue
- Zircon - Blue
Type II gems normally contain clarity
characteristics. The stones most commonly seen in the market include:
- Smoky Quartz
- Zircon - Green
- Sapphire - all colors
- Zircon - Orange