GEMSTONES

Grading :
In the last two decades there has been a proliferation of certification, not only for diamonds but for gemstones as well. There are a number of reputable laboratories which grade and provide reports on gemstones.
International Gemological Institute (IGI), world's largest independent laboratory for grading and evaluation of diamods, jewellery and colored stones.
Gemological Institute of America (GIA), the main provider of education services and diamond grading reports
American Gemological Society (AGS) is not as widely recognized nor as old as the GIA but has a high reputation.
American Gem Trade Laboratory which is part of the American Gem Trade Association (AGTA) the largest trade organization of jewelers and dealers of colored stones
American Gemological Laboratories (AGL) which was recently taken over by "Collector's Universe" a NASDAQ listed company which specializes in certification of many collectables such as coins and stamps
European Gemological Laboratory (EGL).
Gemological Association of All Japan (GAAJ), aka Zenhokyo, the preferred lab within Japan, also very active in the gemological research
Gemmological Institute of Thailand (GIT) is closely related to Chulalongkorn University, and has a good reputation for their gemmological research
Asian Institute of Gemmological Sciences (AIGS), the oldest gemological institute in South East Asia, involved in gemological education and gem testing
Swiss Gemmological Institute (SSEF), founded by Prof. Henry Hänni, offering a high scientific standard, and focusing on coloured gemstones and the identification of natural pearls
Gübelin Gem Lab, the traditional Swiss lab founded by the famous Dr. Eduard Gübelin. Their reports are widely considered as the ultimate judgement on high-end pearls, coloured gemstones and diamonds
Each laboratory has its own methodology to evaluate gemstones. Consequently a stone can be called "pink" by one lab while another lab calls it "Padparadscha". One lab can conclude a stone is untreated, while another lab concludes that it is heat treated [3]. To minimise such differences, seven of the most respected labs, i.e. AGTA-GTL (New York), CISGEM (Milano), GAAJ (Tokyo), GIA (Carlsbad), GIT (Bangkok), Gübelin (Lucerne) and SSEF (Basel), have established the Laboratory Manual Harmonisation Committee (LMHC), aiming at the standardisation of wording on reports and certain analytical methods and interpretation of results. Country of origin has sometimes been difficult to find agreement on due to the constant discovery of new locations. Moreover determining a "country of origin" is much more difficult than determining other aspects of a gem (such as cut, clarity etc.)
Gem dealers are aware of the differences between gem laboratories and will make use of the discrepancies to obtain the best possible certificate [3]. One such example is to make use of the differences in country of origin: a sapphire from Kashmir, India (celebrated for its cornflower blue color) commands four times the price of the same stone from Sri Lanka and twice the price as a similar stone from Burma

Cutting and polishing :
A few gemstones are used as gems in the crystal or other form in which they are found. Most however, are cut and polished for usage as gemstones. The two main classifications are stones cut as smooth, dome shaped stones called cabochons, and stones which are cut with a faceting machine by polishing small flat windows called facets at regular intervals at exact angles.
Stones which are opaque such as opal, turquoise, variscite, etc. are commonly cut as cabochons. These gems are designed to show the stone's color or surface properties as in opal and star sapphires. Grinding wheels and polishing agents are used to grind, shape and polish the smooth dome shape of the stones.
Gems which are transparent are normally faceted, a method which shows the optical properties of the stone’s interior to its best advantage by maximizing reflected light which is perceived by the viewer as sparkle. There are many commonly used shapes for faceted stones. The facets must be cut at the proper angles, which varies depending on the optical properties of the gem. If the angles are too steep or too shallow, the light will pass through and not be reflected back toward the viewer. Special equipment, a faceting machine, is used to hold the stone onto a flat lap for cutting and polishing the flat facets.[8] Rarely, some cutters use special curved laps to cut and polish curved facets.

Gemstone color :
Color is the most obvious and attractive feature of gemstones. The color of any material is due to the nature of light itself. Daylight, often called white light, is actually a mixture of different colors of light. When light passes through a material, some of the light may be absorbed, while the rest passes through. The part that is not absorbed reaches the eye as white light minus the absorbed colors. A ruby appears red because it absorbs all the other colors of white light - blue, yellow, green, etc. - except red.
The same material can exhibit different colors. For example ruby and sapphire have the same chemical composition (both are corundum) but exhibit different colors. Even the same gemstone can occur in many different colors: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colors from yellow to orange-pink, the latter called "Padparadscha sapphire".
This difference in color is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition, they are not exactly the same. Every now and then an atom is replaced by a completely different atom (and this could be as few as one in a million atoms). These so called impurities are sufficient to absorb certain colors and leave the other colors unaffected.
As an example: beryl, which is colorless in its pure mineral form, becomes emerald with chromium impurities. If you add manganese instead of chromium, beryl becomes pink morganite. With iron, it becomes aquamarine.
Some gemstone treatments make use of the fact that these impurities can be "manipulated", thus changing the color of the gem

GEMSTONES

Treatments applied to gemstones :

Gemstones are often treated to enhance the color or clarity of the stone. Depending on the type and extent of treatment, they can affect the value of the stone. Some treatments are used widely because the resulting gem is stable, while others are not accepted most commonly because the gem color is unstable and may revert to the original tone.

Heat :
Heat can improve gemstone color or clarity. Most citrine is made by heating amethyst, and partial heating with a strong gradient results in ametrine - a stone partly amethyst and partly citrine. Much aquamarine is heat treated to remove yellow tones, change the green color into the more desirable blue or enhance its existing blue color to a purer blue.
Nearly all tanzanite is heated at low temperatures to remove brown undertones and give a more desirable blue/purple color. A considerable portion of all sapphire and ruby is treated with a variety of heat treatments to improve both color and clarity.
When jewelry containing diamonds is heated(for repairs) the diamond should be protected with boracic acid; otherwise it could be burned on the surface or even burned completely up. When jewelry containing sapphires or rubies is heated(for repairs) it should not be coated with boracic acid or any other substance, as this can etch the surface; it does not have to be "protected" like a diamond.

Radiation :
Most blue topaz, both the lighter and the darker blue shades such as "London" blue, has been irradiated to change the color from white to blue. Some improperly handled gems which do not pass through normal legal channels may have a slight residual radiation, though strong requirements on imported stones are in place to ensure public safety. Most greened quartz (Oro Verde) is also irradiated to achieve the yellow-green color.

Waxing/oiling :
Emeralds containing natural fissures are sometimes filled with wax or oil to disguise them. This wax or oil is also colored to make the emerald appear of better color as well as clarity. Turquoise is also commonly treated in a similar manner.

Fracture filling :
Fracture filling has been in use with different gemstones such as diamonds, emeralds and sapphires. More recently (in 2006) "Glass Filled Rubies" received a lot of publicity. Rubies over 10 carat (2 g), particularly sold in the Asian market with large fractures were filled with lead glass, thus dramatically improving the appearance (of larger rubies in particular). Such treatments are fairly easy to detect.

Synthetic and artificial gemstones :
Some gemstones are manufactured to imitate other gemstones. For example, cubic zirconia is a synthetic diamond simulant composed of zirconium oxide. The imitations copy the look and color of the real stone but possess neither their chemical nor physical characteristics.
However, lab created gemstones are not imitations. For example, diamonds, ruby, sapphires and emeralds have been manufactured in labs to possess identical chemical and physical characteristics to the naturally occurring variety. Synthetic (lab created) corundums, including ruby and sapphire, are very common and they cost only a fraction of the natural stones. Smaller synthetic diamonds have been manufactured in large quantities as industrial abrasives. Larger synthetic diamonds of gemstone quality, especially of the colored variety, are also manufactured.
Whether a gemstone is a natural stone or a lab-created (synthetic) stone, the characteristics of each are the same. Lab-created stones tend to have a more vivid color to them, as impurities are not present in a lab, so therefore do not affect the clarity or color of the stone. However, natural gemstones are still considered more valuable on average due to their relative scarcity.
The origin of the gemstone also does not affect its categorization as precious or semi-precious. Rubies, sapphires and emeralds are always precious stones, while other gems are considered semi-precious.

GEMSTONES 2

Value of gemstones :There is no universally accepted grading system for any gemstone other than white (colorless) diamond. Diamonds are graded using a system developed by the Gemological Institute of America (GIA) in the early 1950s. Historically all gemstones were graded using the naked eye. The GIA system included a major innovation, the introduction of 10x magnification as the standard for grading clarity. Other gemstones are still graded using the naked eye (assuming 20/20 vision). For the past several hundred years, gemstones have been broken down into two categories; precious and semi-precious. Though today we think primarily of diamond, ruby sapphire and emerald as "precious", these categories are based mainly on fashion and the composition of these two lists has changed frequently over time.
Recently a catchy little phrase, the four c's (color, cut, clarity and carat) was introduced as an aid the help the consumer understand the factors used to grade a diamond. With modification these categories can be useful in understanding the grading of all gemstones. The four criteria carry different weight depending upon whether they are applied to colored gemstones or to colorless diamond. In diamonds, cut is the primary determinant of value followed by clarity and color. Diamonds are meant to sparkle, to break down light into its constituent rainbow colors (dispersion) chop it up into bright little pieces (scintillation) and deliver it to the eye (brilliance). This is a function of cut. In its rough crystalline form, a diamond will do none of these things, it requires proper fashioning and this is called "cut". In gemstones that have color, including colored diamonds, it is the purity and beauty of that color that is the primary determinant of quality.
Physical characteristics that make a colored stone valuable are color, clarity to a lesser extent (emeralds will always have a number of inclusions), cut, unusual optical phenomena within the stone such as color zoning, and asteria (star effects). The Greeks for example greatly valued asteria in gemstones, which were regarded as a powerful love charm, and Hellen of Troy was known to have worn star-corundum. [2]
A factor in determining the value of a gemstone is called water. Water is an archaic term that refers to the combination of color and transparency in gemstones; used hierarchically: first water (gem of the finest water), second water, third water, byewater. [3]
Historically gemstones were classified into precious stones and semi-precious stones. Because such a definition can change over time and vary with culture, it has always been a difficult matter to determine what constitutes precious stones. [4]
Aside from the diamond, the ruby, sapphire, emerald, pearl (strictly speaking not a gemstone) and opal [4] have also been considered to be precious. Up to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a precious stone as well, going back to ancient Greece. Even in the last century certain stones such as aquamarine, peridot and cat's eye have been popular and hence been regarded as precious.
Nowadays such a distinction is no longer made by the trade. [3] Many gemstones are used in even the most expensive jewelry, depending on the brand name of the designer, fashion trends, market supply, treatments etc. Nevertheless, diamonds, rubies, sapphires and emeralds still have a reputation that exceeds those of other gemstones.
Rare or unusual gemstones, generally meant to include those gemstones which occur so infrequently in gem quality that they are scarcely known except to connoisseurs, include andalusite, axinite, cassiterite, clinohumite and bixbite.
Gems prices can fluctuate heavily (such as those of tanzanite over the years) or can be quite stable (such as those of diamonds). In general per carat prices of larger stones are higher than those of smaller stones, but popularity of certain sizes of stone can affect prices. Typically prices can range from 5USD/carat for a normal amethyst to 20,000-50,000USD for a collector's three carat pigeon-blood almost "perfect" ruby.

GEM STONES

Characteristics and classification:
Gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al2O3). Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in. For example diamonds, which have a cubic crystal system, are often found as octahedrons.
Gemstones are classified into different groups, species, and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Emerald (green), aquamarine (blue), bixbite (red), goshenite (colorless), heliodor (yellow), and morganite (pink) are all varieties of the mineral species beryl.
Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and lustre. They may exhibit pleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum.
Material or flaws within a stone may be present as inclusions. The gem may occur in certain locations, called the "occurrence."

GEM STONE

GEMS TIPS

You are welcome to view as much or as little of our gem inventory as you wish!
Please be aware that a search which retrieves a large number of gemstones may take some time to load and to view. If you would like to narrow your search, please use the options described below:

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Types of Gems Amethyst Ametrine Aquamarine Blue Sapphire Blue Tourmaline Blue Zircon Chrome Tourmaline Chrome Diopside Citrine Emerald Garnet Golden Sapphire Green Tourmaline Green Zircon Hessonite(garnet) Imperial Topaz Iolite London Blue Topaz Opal Peridot Pink Tourmaline Plum Grape Garnet Precious Topaz Rhodolite(garnet) Rose Quartz Rubellite(red tourmaline) Ruby Sky Blue Topaz Special Orders Spinel Swiss Topaz Tanzanite Tsavorite(garnet) Turquoise Watermelon Tourmaline White Sapphire Colors Blue Blue/GreenBrown/Orange Cinnamon Color Changing Purple Dark Blue Dark Brown Dark Green Dark Red Green Lavender Light Blue Light Brown Light Green Light Purple Multiple Colors Orange Pink Pink/Green Purple Violet White/Transparent Yellow/Green Yellow/Purple Yellow Shapes Apec Baguette Buff Top Cabochon Chevron Cushion Diamond Emerald Fan Fancy Half Moon Heart Marquise Bar Oval Pear Princess Round Round Lonestar Slice Square Tapered Baguette Tear Drop Trapeze Triangle Trillion
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Types of Gems:
This menu lists our gemstone inventory according to their mineral classifications. For example, if you wish to view all of the available emeralds, then choose that option and then click on "Submit Gemstone Search." If you would prefer to view only those emeralds of a certain cut, carat size, or price range, then use the remaining options listed below.
If you select a type of gemstone, it is not necessary to also select a color unless you are searching for an unusual specimen.
To learn more about the various types of gemstones you can view the Gemstone Types, Properties and Birthstones pages.
Colors:
This menu allows you to choose the color of gemstones you prefer. If you select "red" from the list without specifying a type of gem, you are likely to retrieve examples of rubies, garnets, amethyst, as well as any other gems with a reddish hue. For convenience, the color choices in the search form are not broken down into nearly so many subsets as are normally used to describe gem colors.
Shapes of Gemstones:
If you are shopping for gemstones with a specific shape, then select one of the options under the "Shapes" menu. The default setting retrieves all shapes, so it is not necessary to make a selection.
For more information on gemstone shapes and faceting please view the Shapes page.
Carat Size:
The Carat Size option allows you to select the size [weight] of the stones you wish to view. Available choices are stones of less than 1 carat weight, 1 to 3 carats, 3 to 5 carats, and more than 5 carats.
Price:
If you select a price range it is suggested that you not select a carat size since you might miss a bargain!