Gemstone Guide - Gemstone Education
This Gemstone Education Guide defines the five most essential characteristics of gemstones along with
tips for care. Understanding these characteristics will help you able to shop with confidence.
Color
The color of a gemstone is its most significant characteristic, and many jewelers consider it to be
the most vital evaluation criterion. Gemstones are found in all colors. The color of a gemstone
depends on following three characteristics: hue, saturation, and tone.
Hue
Hue is the basic or unique color of the gemstone. Hue is described as the shade, tint or sensation of
a color. While almost all gemstones have some shades of other colors, the most valuable gemstones are
those that exhibit a pure color and only ‘slight’ hues of other colors in addition to their primary
color.
Saturation
Saturation is a measure of the intensity or purity of a gem's hue or color. A gemstone that is free
of gray or brown hues is considered to be strongly saturated and is more valuable than a gemstone with
lower saturation. Saturation often decides the cut of a gemstone. A high-quality gemstone cut delivers
an even color throughout the stone and exposes the fewest inclusions.
Tone
Tone represents the depth of a gemstone color, ranging from colorless to black. In other words, tone
is described as the relative lightness or darkness of a hue. Gemstone tone is described as ‘light’,
‘medium-light’, ‘medium’, ‘medium-dark’, and ‘dark’. Medium-light to medium-dark tone is considered to
be the most valuable range.
All the above three characteristics are associated with each other and play very crucial roles in
determining the gemstone’s color. The more intense the color, the greater the value. This does not
mean darker, but more intense.
Clarity
Clarity is a term used to describe the absence or presence of flaws inside or on the surface of a
gemstone. A flawless gemstone is rare and usually expensive. Most gemstones have inclusions, or tiny
mineral flaws, that can be seen under magnification or by the careful eye. A gemstone may have
inclusions, cracks, spots, clouds, or any other blemish or imperfection.
For diamonds, a clarity Grade Scale from F (Flawless) to I3 (Included 3) is used, whereas for other
colored gemstones a different grading scale is used. Colored stones are classified into three ‘Types’,
which are defined as below:
Type I
Type I colored stones include stones with very little or no inclusions. This category can include
Aquamarine, Blue Topaz, Zircon, Morganite, Tanzanite, etc.
Clarity in the Type I group is classified as VVS (minute to detectable), VS (minor), SI1
(noticeable), SI2 (obvious) or I (included)
Type II
Type II colored stones include stones that often have a few inclusions. This category can include
Corundum, Garnets, Iolite, Peridot, Quartz (Amethyst, Citrine, Ametrine), Ruby, Sapphire, Spinel, etc.
Clarity in the Type II group is classified as VVS (minor), VS (noticeable), SI1 (obvious), SI2
(prominent), or I (prominent, affecting appearance).
Type III
Type III colored stones includes stones that usually always have inclusions. This category can
include Emeralds, Tourmaline, etc.
Clarity in the Type III group is classified as VVS (noticeable), VS (Obvious), SI1 (prominent), SI2
(more prominent), or I1 (affecting appearance or durability).
Cut
A good cut is key to giving a gemstone its beauty and brilliance. A gemstone's cut refers to its
proportions and symmetry. The stone should be symmetrical in all dimensions so that it will appear
balanced, and so that its facets will reflect light evenly, which will provide good brilliance to the
stone. A well-cut faceted gemstone reflects light back evenly across its surface area when held face
up. If the stone is too deep and narrow, surface area will be dark and if it is too shallow and wide,
parts of the stone will be washed out and lifeless.
While cutting, the color of a gemstone should also be considered for optical efficiency. If a stone's
color is highly saturated, a shallow cut will allow it to pass more light, while a deeper cut may
increase the vividness of a less saturated gem. There is no generally accepted grading system for
gemstone cut.
Cabochon Cut
In the cabochon cut, the upper surface of the stone is smoothed and rounded into a simple curve of
any degree of convexity; the lower surface may be concave, convex, or flat. All the remaining cuts
have flat facets.
Table Cut
In the table cut, the facets of the natural octahedron of the stone are ground to smoothness and
polished. One facet, the table, is ground much larger than any other and made the top of the gem,
while the opposite facet, the culet, is left quite small.
Rose Cut
The rose cut consists of a flat base and (usually) 24 triangular facets—resembling a cabochon with
facets.
Brilliant Cut
The brilliant cut is scientifically designed to bring out the maximum brilliancy of the stone. The
crown of a brilliant consists of a table and 32 smaller facets, of which 8 are quadrilaterals and 24
are triangles; the base, a culet and 24 larger facets, of which 8 are quadrilaterals and 16 are
triangles. The base and crown are separated by a girdle. The brilliant cut has certain proportions—in
general, the depth of the crown is one third the depth of the stone and the width of the table one
half the width of the stone.
Other Cuts
In addition to the above defined cuts, stones are also cut in a variety of square, triangular, step,
emerald, and trapezoidal faceted cuts. The use of such cuts is largely determined by the original
shape of the stone. Large rubies, sapphires, and emeralds are often cut square or rectangular with a
large table facet surrounded by a relatively small number of supplementary facets.
The process of cutting and polishing gems is called gem cutting or lapidary, while a person who cuts
and polishes gems is called a gem cutter or a lapidary (sometimes lapidarist). Few gemstones such as
pearls and coral (usually referred to organic minerals) are not cut at all and many times left in
their natural state. However, it is customary to polish these items, as with all gemstones. The
quality of a gemstone's cut can have a dramatic impact on how it looks but only a small impact on the
price per carat.
Size
Similar to diamonds, a gemstone’s weight is also measured in carats where one carat equals 200
milligrams. However, in case of gemstones, this may not give an accurate idea of its size, because
different types of stones have different densities Two gemstones of the same carat weight may be
different in sizes. For example, a 1 carat Sapphire or Ruby will be smaller than a 1 carat Emerald,
though they have the same carat weight, because Sapphires and Rubies are denser than Emeralds. At the
same time, a 1 carat Diamond will be larger than a 1 carat Ruby as a Diamond is less dense than a
Ruby. Gemstones can also be measured in dimensions (diameter, length, and width).
Illustration of gemstone dimensions (L/W = Length to
Width Ratio)
Asscher
Baguette
Cushion
Emerald
Heart
Marquise
Oval
Pear
Princess
Radiant
Round
Trillion
In the case of gemstones, larger stones are not always more valuable. The rarity of a certain size
will determine the value of a gemstone. A gem that is available naturally in weights of 10 carats or
more may be less valuable than one that is rarely available in large sizes.
Enhancements
- N – The ‘N’ symbol appears on the chart only for natural stones
which are not currently known to be enhanced.
- E – The ‘E’ symbol appears on the chart only for those
gemstones, which are routinely enhanced. The type of enhancement covered by this symbol is indicated
on the following chart.
- Third category covers those gemstones which are treated in a non-traditional manner and that
enhancement process or code is not covered under ‘N’ & ‘E’
symbols.
Gemstone Enhancement is a treatment process other than cutting and polishing that improves the
appearance (color / clarity), durability or availability of a gemstone. This treatment covers heating,
oiling, irradiation, waxing, dying, bleaching etc.
There are many ways to enhance the appearance and durability of gemstones. Some of these treatments
or enhancements are permanent whereas others are temporary. Gemstone enhancement has become such a
common as well as accepted practice that experts believe the vast majority of stones are treated in
some way. It's important to remember that most gemstone enhancements greatly improve the appearance -
and hence the value - of a stone.
All gemstones can be divided into 3 basic categories:
Gemstone Enhancement Information
B - Bleaching: The use of chemicals or other agents to lighten or remove a
gemstone's color. Pearls and ivory also may be bleached to lighten their color.
C - Coating: The use of such surface enhancements as lacquering, enameling, inking,
foiling, or application of films to improve appearance, provide color or add other special effects.
D - Dyeing: The introduction of coloring matter into a gemstone to give it new
color, intensify present color or improve color uniformity.
F - Filling: As a by-product of heat enhancement, the presence of solidified borax
or similar colorless substances which are visible under properly illuminated 10X magnification.
G - Gamma/Electron Irradiation: The use of gamma and/or electron bombardment to
alter a gemstone's color; may be followed by a heating process.
H - Heating: Heating is one of the most common treatments used to enhance the
natural beauty of colored gemstones. It is a permanent process that can dramatically improve the color
and/or clarity in a number of stones, including sapphires, rubies, diamonds, aquamarine, amethyst,
tanzanite, topaz, tourmaline and other stones.
I - Infilling: The intentional filling of surface breaking cavities or fractures
usually with glass, plastic, opticon with hardeners and/or other hardened foreign substances to
improve durability, appearance and/or add weight.
Care
Gemstones are generally hard and durable in nature but given our day-to-day activities, our gemstone
jewelry will get dirty and soiled. Gems can be scratched, chipped or dulled if not handled correctly.
With proper care, they can last a lifetime and can even be handed down as heirlooms to future
generations without losing their shine and sparkle. Organic gems like pearls, amber, and coral require
special care because they are porous.
Here are some tips that will help you to preserve the life and beauty of your gemstones:
Cleaning of Colored Gemstone Jewelry
Regular cleaning of Gemstone Jewelry is essential to maintain the shine and brilliance of the gems.
On wearing them, they get dirty as you use various skin and body care regimen such as soaps, lotions
and even our skin's natural oils. Even when you are not wearing them, they collect dust. If you are
cleaning your gemstone jewelry by your own then it will take few minutes to clean the same but before
cleaning, you must be aware about the cleaning at home and cleaning by a professional jeweler:
- To clean gemstone jewelry, first wipe it with a soft cloth to remove any dirt. You can use a small
soft brush such as an eyebrow or lip stick brush, soap and water to clean your gemstone jewelry. Do
not use toothpaste or any other abrasive cleaner on stones or the mounting. Simply make a bowl of
warm sudsy water with a mild detergent and gently place your jewelry pieces in the mixture. Never
use boiling or hot water to clean gems. Brush the gemstones with the soft bristles of the brush
while they are in the suds. You will need to make certain that you rinse them clear of the suds
after cleaning them. After this process, use a soft cloth or a jewelry polish cloth to pat them dry.
- You can also use liquid jewelry cleaners which are sold by many department stores and jewelry
stores. You can find these liquid jewelry cleaners in kit form. Follow all the written precautions
and instructions for cleaning. A home ultrasonic cleaner should be used with caution. It can be used
to clean ruby, sapphire, diamond, iolite, amethyst, citrine, garnets, iolite, chrysoberyl, and
unadorned gold jewelry but it may damage gems like emerald, pink tourmaline, peridot, pearls, coral,
lapis lazuli, malachite, turquoise, and any gem that has many inclusions. When in doubt, don’t use
it.
- It is also a good idea to have your jewelry cleaned once a year by a professional jeweler, so he
will check the security of the settings. He will also give advice for repair of loose or bent prongs
which hold your gemstones in place. This will prevent your gem from falling out of its setting and
becoming lost. The jeweler will usually give your gemstone a professional ‘shine and polish’.
- Ultrasonic cleaning machines are available to clean jewelry by bombarding it with sound waves.
This vibration shakes off dirt, but the vibrations can also cause damage to the gemstone, especially
brittle stones like emeralds. Any stone inclusions can be greatly enlarged by the shaking, making
the gem less attractive and valuable. For gemstones, caution is recommended when using the
ultrasonic cleaners.
Storing of Colored Gemstone Jewelry
The storing of gemstone jewelry is also important as a gem can scratch another gem, as well as other
jewelry pieces. Storage of gemstone jewelry should include the following precautions:
- Gemstone jewelry should be stored individually in a soft cloth pouch to ensure that a gem should
not scratch other gems or other jewelry.
- Gemstone jewelry pieces are best stored in a fabric-lined jewel case or in a box with compartments
or dividers.
Precautions for Wearing Colored Gemstone Jewelry
- You should not wear gemstone jewelry while playing sports, working on heavy equipment or relaxing
in a pool or spa (especially if you are in chlorine regularly). A gemstone can be chipped by a hard
blow, and even everyday activity can loosen jewelry settings.
- You should avoid a situation where your gemstones come in contact with chlorine bleach, hair spray
or other chemicals because they can pit or discolor the mounting. Put on your gemstone jewelry after
using makeup, perfume or cologne, and hair products.
- If you have antique or vintage jewelry, perhaps passed down to you, then consider resetting the
gems into a modern style jewelry piece. Gems should be worn and enjoyed and not kept locked away in
a safety deposit box.
If you will follow the above-mentioned care tips, then your gemstone jewelry will always shine and
sparkle like new.