Buyer's Guide

Gems have always been worn for personal adornment and given as the most luxurious gifts. Wealthy people are especially looking for tangible assets that are portable and easily concealed due to their size. Gems have also been valued as an investment throughout time.

Fabulous rubies, brilliant sapphires, huge emeralds, garnets, and other gems bring to mind images of beauty and great riches. Gemstones have long fascinated the human population. They have inspired myths, curses, and have even been used as medicine. All the gemstones we so greatly treasure and admire come from various depths and locations in the earth’s crust.

Varied and various, there are many gemstones in this world but each one is unique in its own way. More than just beautiful, these striking gems are valuable due to their dazzling beauty and rarity.

There are more than 4000 naturally occurring minerals on this Earth that we know of. These minerals commonly develop from the cooling of molten rock or magma but it’s what they will become that is particularly intriguing.

 Historically, gemstones have been categorized into two distinctive classes; precious and semi precious stones. While there are many numbers of semi precious gems, opals, rubies, sapphires and emeralds continue to be deemed precious. 





The MOHS Hardness Scale is used as a convenient way to help measure the relative hardness of a mineral by its resistance to scratching. From softest to hardest, the ten minerals of the Mohs scale are  talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum, and diamond (measuring 10 on the scale).


Optical properties are those related to the behavior of light, on, or in, a gemstone.
Some of these can be seen, and even quantified, with the naked eye alone. Three such characteristics are: luster, transparency, and color. The study of these factors, and their use in gem identification and evaluation, is sometimes called optical gemology.
Other characteristics are revealed, or measured, only through the use of special instruments. Some of these include: refractive index, optical character, birefringence, pleochroism, dispersion, reaction to ultraviolet light and selective absorption. When these properties of gems are analyzed and measured, one is engaging in laboratory gemology.



 Describes gemstones that allow light to pass completely through
the stone. You can easily see through a transparent stone.


Describes gemstones that allow you to see into. Some light
passes through the stone but not clearly through it. The stone can be
described as cloudy or silky.


Describes gemstones that one may not see through at all. Turquoise
is a good example of an opaque stone.


Describes a type of dichroism seen in highly dispersed systems with little opacity.  The material appears yellowish-red in transmitted light and blue in the scattered light perpendicular to the transmitted light.  The phenomenon is named after the appearance of opals and is an example of the Tyndall effect. 


An optical phenomenon displayed by some rubies, sapphires, and other gems
(e.g. garnet, diopside, spinel) of an enhanced reflective area in the shape of
a "star" on the surface of a cabochon cut from the stone.


Known as chatoyancy, or cat's eye effect, is caused by inclusions
of fine, slender parallel mineral fibers in the gemstone that reflect light in
a single band. Of all the gemstones that exhibit cat's eye, Chrysoberyl Cat's
Eye is the best known.


In gemology, an inclusion is a characteristic within a gemstone, or reaching its
surface from the interior.
Inclusions are one of the most important factors when it comes to gem valuation. In many gemstones inclusions affect the clarity of the gem. Inclusions let you know that the gems are natural earth-mined and sometimes even show traces of origin but too many inclusions may diminish the value of a stone. In some gems, however, such as star sapphires, the inclusion actually increases the value of the stone.
Most Emeralds have some inclusions which are referred to as "the garden". Inclusions are accepted in the following gems listed under gemstones type 1 without detracting from their value.
Also note many of the inclusions seen in loose gemstones disappear when set in jewelry. Viewing a loose gemstone will reveal more inclusions than a stone in its setting.


Stones that normally have small inclusions that do not detract from value. Alexandrite, Emerald, Peridot, Ruby, Sapphire, Spinel, Tourmaline, Red Zircon, Tsavorite, Fluorite.Yellow and Parti-colored Tourmaline.


The following gemstones are typically inclusion free, even minor inclusions detract from their value.
Amethyst, Beryls(Aquamarine,Morganite), Citrine, Smoky Quartz, topaz, Chrysoberyl, Tanzanite, green Tourmaline.


In today’s gem markets as science and gemology evolves many stones are treated to improve appearance. Treatments include; Heating, Fracture Filling, Cobalt, Resin, Beryllium or Borax Flux. Oil treatments, etc. depending on type of gem. There is nothing wrong with purchasing or selling a treated long as treatments are stable/permanent and disclosed.

Gemstone enhancements are procedures applied to gems to improve their appearance and wear-ability.The most common form of enhancement is Heating. For example, jewelers should inform their customers that rubies and sapphires are “probably heat treated,” since heating is normal and accepted common practice for corundum gems.Treatments may effect price in a positive or negative way but that's not always the case. We state enhancement types in all of our descriptions.

Lab reports from our accredited labs can also be obtained.We want our customer 100% satisfied with any purchase from The Gem Portal.


Enhancement Type


Heat (H)
Beryllium  (BE)
Irradiation (IR)
Surface Diffusion (SD)
Fracture Filling (FF)
Borax Flux (BF)
Cobalt/Resin (C/R)



Gems that are the same carat weight can differ in physical size and vice versa. For example, a 2-carat citrine is dimensionally larger than a 2-carat sapphire, and an emerald that measures 8X6 millimeters weighs less than a ruby of the same dimensions. That’s because the gems have different densities.Density is the relationship between a gemstones weight and physical size. Keep this in mind when judging the size of a gem by its carat weight only. 


Ideally, you should segregate gems by color. Place warm red stones like ruby in one area using a yellowish incandescent light. emerald, peridot, tsavorite, or other predominantly green stones appear best when subjected to greenish or blueish daylight-equivalent light sources or actual daylight itself. Blue Sapphires look great in most fluorescent lights.

“The colored stone industry, unfortunately, has almost no standardization on the subject of lighting. Big dealers have been known to usen“buying lights” and “selling lights.” They use poor color-rendering lights for buying and color-exaggerating lights for selling.

Note a digital image of a gemstone unfortunately cant always capture the true beauty of a gemstone. The light source gems are viewed in plays a big part. At The Gem Portal we are using three common light sources; incandescent, fluorescent, and sun light. We believe using all three captures the stones true beauty in the lights that people use in daily life to view their gemstone.


The refractive index of a gemstone provides the most important piece of information to anyone seeking to identify an unknown stone. It is a constant that is measurable to four significant figures (i.e. 3 decimal points) and can allow gemstones to be identified even when their R.I’s differ only very slightly.

Gem Type

Refractive Index


2.65 - 2.69




1.96 - 2.01


1.76 - 1.77


1.76 - 1.77




1.71 – 1.74


1.65 - 1.69


1.62 - 1.64


1.61 - 1.62


1.57 - 1.60




1.54 - 1.55


1.54 - 1.55


1.37 – 1.47


The bending of light when it passes from a rarer medium (Air) into a denser medium (Gemstone).


Light passing through a substance is bent from its original path, but emerges as a single ray. Only occurs in gem minerals belonging to the cubic crystal system or amorphous materials.


Light passing through a substance is split into two rays, which travel at different velocities causing differing amounts of refraction. Occurs in gem minerals belonging to all other crystal systems.


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