Gemstone Clarity Grades GIA

 


 

Type 1 Gemstones

(These gemstones are typically inclusion free)

Amethyst, Beryl (except Red Beryl and Emerald), Citrine, Chrysoberyl (except Alexandrite), Garnet (except green and orange), Kunzite, Topaz, Green Tourmaline, Tanzanite, Zircon

VVS  minute to not detectable
VS     minor
SI1    NOTICEABLE to obvious
SI2    OBVIOUS to noticeable
I1      
prominent to moderate affect on appearance or durability
I2      prominent to
severe affect on appearance or durability
I3      prominent to
severe affect on beauty, transparency, or durability

Type 2 Gemstones

(Gemstones that normally may have a few inclusions)

Alexandrite, Andalusite, Iolite, Peridot, Rhodolite, Ruby, Sapphire, Spinel, Tourmaline, and Tsavorite

VVS  minor
VS     NOTICEABLE to obvious
SI1    noticeable to OBVIOUS
SI2    obvious to prominent
I1      prominent - moderate affect on appearance or durability
I2      prominent - severe affect on appearance or durability
I3      prominent - severe affect on beauty, transparency, or durability

Type 3 Gemstones

(Gemstones that normally do not come clean)

Emerald, Red Beryl (Bixbite), and Rubellite (Red Tourmaline).

VVS  NOTICEABLE to obvious
VS     noticeable to OBVIOUS
SI1    obvious to prominent
SI2    obvious to PROMINENT
I1      prominent to considerable affect on appearance or durability
I2      prominent to severe affect on transparency or durability
I3      prominent to severe affect on beauty, transparency, or durability

 

Mohs Hardness Scale

 

1.

Can be scratched easily with a fingernail.

Talc: 1

Sulfur: 1 ½-2

2.

Can be scratched with a fingernail.

Gypsum: 2

Mica: 2 - 2 ½

3.

Can be scratched with a coin.

Calcite: 3

Pearl: 3-4

4.

Can be scratched easily with a knife; cannot scratch glass.

Rhodochrosite: 4

Fluorite: 4

5.

Can be scratched with a knife; can just scratch glass.

Lapis Lazuli: 5-6   Apatite: 5

Turquoise: 5-6      Opal: 5 ½-6 ½

6.

Can be scratched with a steel file; easily scratches window/bottle glass.

Feldspar: 6-6 ½     Pyrite: 6 ½     

Tanzanite: 6 ½-7   Zircon: 6 ½-7 ½

Peridot: 6 ½-7       Moonstone: 6-6 ½

7.

Easily scratches metal, glass, and softer stones.

Quartzes: 7          Tourmaline: 7-7 ½

Garnet: 7-7 ½        Beryls: 7 ½-8

8.

Scratches Quartz and softer stones.

Topaz: 8

Chrysoberyl: 8 ½

9.

Scratches Topaz and softer stones.

Ruby: 9

Sapphire: 9

10.

Scratches Ruby and Sapphire.

Diamond: 10

 

**Gemstones with a Mohs Hardness factor under 7 should ideally be set into pendants and earrings. It is not wise to set them in ring or bracelet settings.**

 

Pearl Grades**

AA-Grade: The surfaces of these Pearls are nearly blemish-free. They have great luster and exhibit depth.

A-Grade: The surfaces of these Pearls show a few insignificant blemishes. Their luster is good, and exhibits some depth.

A/B Grade: Surface blemishes are seen easily. The luster of the Pearl is moderate. Even though this grade is not perfect, it is still beautiful and offers the most economical value.

**There are no official guidelines for the grades of Pearls, but these are the most common ones used by manufacturers in the gemstone industry.

**Cultured Pearls are produced by inserting a Mother-of-Pearl bead into a live oyster and then returning it to the water, usually into "farming beds" to grow its nacre coating.

Types of Pearls

Akoya Cultured Pearls: (Saltwater) They are beautiful top quality cultured saltwater Pearls. They exhibit a deeper luster than is possible in freshwater Pearls. Because of their higher quality and dwindling supplies, these gems hold their value better than any other Pearls. They are most commonly grown in Japan and China. They are available in white (bleached) and black (dyed) colors.

Tahitian Pearls ~ South Seas Pearls: (Saltwater) They These all natural elegant and expensive Pearls are found in the saltwater seas around French Polynesia. They may be found in naturally occurring shades of black, silver, gold, and cream. They also display overtones of a variety of colors in-between. The most well-known colors of these magnificent Pearls are the darker shades, which range in color from black to graphite to metallic silver, with bluish, purple, and/or green overtones. Some may refer to them as “peacock” in color. They are cultivated from a black-lipped variety of oyster (pinctada maxima) which is found in the seas of French Polynesia. Tahitian Pearls are widely regarded as symbols of luxury and perfection. They have been referred to as the “Queen of Pearls.”

Freshwater Pearls: These Pearls are the most economical and common of the Pearl varieties. They also come in a variety of colors, sizes, and shapes. Most of these Pearls are grown in China. They offer a beautiful and economical alternative for designing Pearl jewelry. The majority of these Pearls are either bleached or dyed to attain the variety of colors. Some shades are naturally colored, such as a few shades of peach and lavender. These Pearls may also be shaped, carved, or faceted.

Mother of Pearl: These pearls come from the inner shell of a mollusk and the layers of nacre built upon it. They are considered to be an organic-inorganic composite material, which is strong and resilient. Chief sources of Mother of Pearl are oysters found in warm and tropical seas. They may also be harvested from freshwater mussels. They are available in many colors and shapes. They may be natural in color or bleached or dyed to obtain the colors of choice.

Mabe Pearls: They are also known as “Blister Pearls.” They are formed against the shell in a blister-like shape. Mabe Pearls are most frequently produced within saltwater oysters within the regions of Japan, Indonesia, Australia, and French Polynesia. The finest quality of Mabe Pearls come from the Amami Ohima Islands off the southern coast of Japan. Due to the way they are formed, they will have one flat side. They are also available in many colors and shapes. They may be natural in color or bleached or dyed to obtain the colors of choice.

The Structure of Pearls


 

Types of Opal

There are four types of "Gem Opal," also known as "Precious Opal." They are White Opal, Black Opal, Crystal, or Water Opal, and Fire Opal. There are also several other varieties of Opal with physical properties that vary considerably, which do not fall under the category of "Gem Opal" or "Precious Opal." They are known as “Common Opal.” Several varieties of Opal are described below.

**Precious Opal Varieties: This group’s special characteristic is exhibiting a "play-of-color." These rainbow-like hues change with the angle of observation. Tiny spheres of Cristobalite layered in silicious jelly cause the diffraction and interference patterns which produce the play-of-color. Over time the play-of-color may diminish due to loss of water in the Opal. It can be temporarily restored by treating the stone with saturation of oil, epoxy, resin, or water. Opal is often impregnated with plastic to improve its appearance. Opals are known to dry out easily and crack, or craze. It is wise to keep gemstone quality Opal and cabochons dry for at least one year prior to cutting or setting it, as it can easily crack during setting. The aging process may be avoided by storing it in moist absorbent cotton wool. Listed below are types of Precious Opal. Noted sources of these Opals are: Slovakia, Lightning Ridge and and White Cliffs in New South Wales, Australia, Coober Pedy and Andamooka in South Australia, and many locations in Queensland, Australia. Other noted deposits are in Brazil, Ethiopia, Guatemala, Honduras, Indonesia, Japan, Mexico, Russia, Nevada, and Idaho.

White Opal: A precious Opal of white or otherwise light basic body color with color play.   

Black Opal: Precious Opal with dark gray, dark blue, dark green, and gray-black basic color and color play. Deep black is an exception. Black Opals are rarer than White Opals.

Crystal Opal ~ Water Opal: This type of Opal is transparent with strong color play on a colorless vitreous surface.

Fire Opal: This type of Opal gets its name from its orange to red color. It often does not show any play-of-color. The specimens that do display color play are rare. The play-of-color in Fire Opal is referred to as “Contra Luz” color play. The body color of these Opals can vary from nearly colorless to shades of yellow, orange, and nearly red. They are usually milky and turbid looking in appearance. The best quality Fire Opals are clear and transparent, so they are usually suitable for faceting. They are very sensitive to stress, so much care must be taken when faceting and setting these gemstones. Fire Opal deposits can be found in Mexico, Brazil, Guatemala, Western Australia, and the United States. These beautiful Opals are often hand carved into many types of figurines.

Boulder Opal: This is Precious Opal with a dark base surface, color play, and high density. It occurs as a pebble rock, where Opal fills in hollows or seams.

Opal In Matrix: These Opals have banded growth or leafed inclusions of Precious Opal with and/or in the matrix rock.

Harlequin Opal: This is a type of Precious Opal which is transparent to translucent with effective mosaic-like color patterns. It is considered to be among the most desirable of Opals.

Jelly Opal: This is a bluish-gray Precious Opal with only a small amount of play-of-color.

**Common Opal Varieties: (Potch) This type of Opal is opaque, rarely translucent, and shows no play-of-color. It can be found under many different trade names, some of which are listed below. It can be found in many different areas around the world.

Agate Opal (Opal Agate): This is Agate with light and dark Opal layers.

Angel Skin Opal: This is a misleading name for Palygorskite, which is an opaque, whitish to pink colored silicate mineral.

Wood Opal: (Zeasite) This is a yellowish or brownish Opal which is actually Petrified Wood.

Honey Opal: This is a honey-yellow colored translucent Opal. These stones may exhibit Cat’s Eyes due to fibrous inclusions.

Hyalite Opal: (Glass Opal) (Waterstone): This is a colorless, water-clear type of Opal with a strong sheen. It normally appears in botryoidal “bubbles,” and is known to fluoresce a brilliant bright green under shortwave UV light. A rare variety of pleochroic Hyalite Opal has been found in the southwestern United States. It is colorless in a room without any light present. As you move it closer and closer to stronger light sources, it goes from a pale green to a bright lime green color.

Hydrophane: This is a milk Opal, which has turned turbid due to the loss of water. Through absorpsion of water, it can become translucent again and have color play.

Porcelain Opal: This is a white, opaque milk Opal.

Moss Opal: This is a milk Opal containing dendrites.

Girasol Opal: This type of Opal is almost colorless. It is transparent and has a bluish opalescence, or pearlescence, especially when it is back-lit.

Prase Opal: (Chrysopal) This is an apple-green Opal, which is sometimes used as a substitute for Chrysoprase.

Wax Opal: This is a yellow-brown Opal with a wax-like luster.

Liver Opal: (Menilite) This is very similar in appearance to Wax Opal, but a bit darker (browner) in color.

Pineapple Opal: This is actually an Opal pseudomorph after Ikaite, which resembles a Pineapple. It is found only in New South Wales, Australia.

***Cultured Opal: These Opals have been synthesized in a lab. Chemically they are indistinguishable from real opals. Their physical properties and chemical composition are similar to that of natural Opal. The synthesized material is distinguishable from natural opal under magnification. Patches of color are seen in a chicken wire-like pattern. Synthetic Opals commonly contain plastic stabilizers.

 

The Anatomy of a Gemstone


 

The Most Popular Gemstone Cuts


 

Dispersion of Color


 

**This illustration shows how dispersion of the original white light breaks down into the spectral colors when going through a prism. It will do the same thing when passing through a gemstone, as seen below. The level of dispersion varies from mineral to mineral. Those with the highest levels of dispersion will exhibit more “fire” and brilliance of colors.

 


 

 

Trade Names For Gemstone Imitations and Synthetics

 

Cubic Zirconia

Absolute, Allanite, Cerene, CZ, Cubic Z, Cubic Zirconium, Diamon-Z, Diamon-QU, Diamonair II, Diamonesque, Diamonique II, Diamonite, Diamondite, Diconia, Djevalite, Fianite, Phyanite, Shelby, Signity, Singh Kohinoor, Zirconia, Zirconium

 

YAG (Yttrium Aluminum Garnet)

Alexite, Amatite, Astrilite, Circocolite, Dia-Bud, Diamite, Diamogen, Diamonair, Diamone, Diamonique, Diamonite, Diamondite, Diamonte, Di’Yag, Geminair, Kimberly, Nier-Gem, Regalair, Replique, Somerset, Triamond, Yttrogarnet

 

Strontium Titanate

Bal De Feu, Diagem, Diamontina, Dynagem, Fabulite, Jewelite, Lustigem, Marvelite, Pauline Trigere, Rossini Jewel, Wellington, Zenithite

 

Synthetic Sapphire

Crown Jewels, Diamondite, Walderite, Violite

 

Synthetic Spinel

Alumag, Corundolite, Erinide, Magnalux, Rozircon, Strongite

 

Synthetic Rutile

Diamothyst, Kenya Gem, Titania

 

Glass

Royalite

 

Doublets

Lasergem, Carnegiegem, Diarita

 

Created Moissanite

(Charles and Colvard) Moissonite

 

Simulated Alexandrite

Zandrite, Color Change Corundum (Lab Grown)

 

Synthetic Lab Grown Gems

Multiple Colors of Sapphire (Faceted and Cabochons), Star Sapphire and Ruby (Cabochons), Simulated Opal (Lab Grown)

 

Chatham High Quality Lab Grown Synthetic Gemstones

Emerald, Alexandrite, Padparadscha Sapphire, Ruby, Sapphire

 

**There are also many other simulants and synthetics available on the market which are absolutely beautiful. They can be very cost efficient if you cannot afford the natural gemstones. As with anything else, be fully aware of what you are purchasing. There are even many fake and/or "manufactured" minerals out there!

 

False and Misleading Names of Some Gemstones

 

False Gemstone Name

Preferred Gemological Name

 

 

Adelaide Ruby

Almandite Garnet

African Emerald

Green Fluorite

Alaska Diamond

Rock Crystal (Clear Quartz)

American Jade

Green Idocrase

American Ruby

Pyrope or Almandite Garnet

Arizona Ruby

Pyrope Garnet

Arizona Spinel

Red or Green Garnet

Arkansas Diamond

Rock Crystal (Clear Quartz)

Balas Ruby

Red Spinel

Blue Alexandrite

Color Change Sapphire

Blue Moonstone

Artificially Blue Tinted Chalcedony

Bohemian Chrysolite

Moldavite (Meteoric Glass)

Bohemian Diamond

Rock Crystal (Clear Quartz)

Bohemian Ruby

Pyrope Garnet or Rose Quartz

Brazilian Aquamarine

Blue-Green Topaz

Brazilian Ruby

Red or Pink Topaz

Brazilian Sapphire

Blue Tourmaline (Indicolite)

California Ruby

Hessonite Garnet

Candy Spinel

Almandite Garnet

Cape Chrysolite

Green Prehnite

Cape Ruby

Pyrope Garnet

Ceylon Diamond

Colorless Zircon

Ceylon Opal

Opal-like Moonstone

Copper Lapis

Azurite

German Diamond

Rock Crystal (Clear Quartz)

German Lapis

Artificially Blue Tinted Chalcedony

Gold Topaz

Citrine

Indian Jade

Aventurine

King’s Topaz

Yellow Sapphire

Korean Jade

Serpentine

Lithia Amethyst

Kunzite (Pink Spodumene)

Lithia Emerald

Hiddenite (Green Spodumene)

Madeira Topaz

Citrine

Marmarosch Diamond

Rock Crystal (Clear Quartz)

Matura Diamond

Colorless Fired Zircon

Mexican Diamond

Rock Crystal (Clear Quartz)

Mexican Jade

Artificially Tinted Green Marble

Montana Ruby

Red Garnet

Oriental Amethyst

Violet Sapphire

Oriental Hyacinth

Pink Sapphire

Oriental Topaz

Yellow Sapphire

Palmyra Topaz

Brown Synthetic Sapphire

Salmanca Topaz

Citrine

Saxon Chrysolite

Greenish-Yellow Topaz

Saxon Diamond

Colorless Topaz

Serra Topaz

Citrine

Siamese Aquamarine

Blue Zircon

Siberian Chrysolite

Demantoid Garnet

Siberian Ruby

Red Tourmaline (Rubellite)

Simili Diamond

Imitation Glass

Slave Diamond

Colorless Topaz

Smoky Topaz

Smoky Quartz

Spanish Topaz

Citrine

Strass Diamond

Imitation Glass

Transvaal Jade

Green Hydrogrossular Garnet

Ural Sapphire

Blue Tourmaline (Indicolite)

Viennese Turquoise

Artificailly Blue Tinted Argillaceous Earth

 

**Source: “Gemstones of the World” by Walter Schumann

 

How Do Minerals, Crystals, & Gems Get Their Colors?

 

Color results from a mineral’s chemical composition, impurities that may be present, and flaws or damage in the internal structure. Most minerals are usually white or colorless in a pure state. Many impurities can color these minerals and make their color variable. Some crystals get their color from growth imperfections. Growth imperfections interfere with light passing through the crystal making it appear darker or nearly black.

 

**Idiochromatic minerals are "self colored" due to their composition. The color is a constant and predictable component of the mineral.

 

**Allochromatic minerals are "other colored" due to trace impurities in their composition or defects in their structure. In this case, the color is a variable and unpredictable property of the mineral.

 

**Pseudochromatic minerals are "false colored" due to tricks in light diffraction. The color is variable but a unique property of the mineral, such as the colors produced in precious opal and the shiller reflections in Sunstone and Labradorite.

 

**The most common trace elements/coloring elements in minerals are: Beryllium, Chromium, Cobalt, Copper, Iron, Lithium, Manganese, Nickel, Sulfur, Titanium, Uranium, and Vanadium.

 

Why Do Gemstones Have Different Colors?

 

Color is the most important characteristic of gemstones, though in the case of most Diamonds it is the absence of color which is most important. What is responsible for the variations in color?

 

Color is produced by the way a gemstone absorbs light. Light is an electromagnetic vibration at certain wavelengths, but the human eye can only perceive certain wavelengths. The field of the visible color spectrum includes red, orange, yellow, green, blue, and violet.

 

There are several different reasons why the various gemstone varieties absorb light differently. Some gemstones are said to be idiochromatic or self-colored. They absorb certain wavelengths of light due to characteristics of their chemical structure. Most gemstones are allochromatic. They are colored by impurities or trace elements in their crystal structure.

 

If all the different wavelengths of light pass through a gemstone, it will appear colorless. On the other hand, if the gem material absorbs all the light, it will be appear black. If a stone absorbs all wavelengths except those in the red part of the spectrum, the gem will appear red.

 

The relationship between a chemical impurity and a gemstone color is not a simple one. Sometimes a similar color can result from different trace elements. Also, a single trace element can produce different colors in different gem varieties. This is because there is a complex relationship between the gem's crystal structure and the trace elements.

 

Another way in which gemstones acquire color is through human intervention in the form of gem treatments. Heat treatment is often used to change the chemical state of an impurity to deepen or lighten color, reduce a certain hue, or improve clarity. Gemstones are also dyed, treated with chemicals, coated with chemicals or metals, irradiated, and artificially colored in many other ways to alter their appearance. Mystic Topaz, Aqua Aura Quartz, along with many other trade names for various colors of topaz and quartz, are examples of gemstones that are surface treated with various metals to exhibit quite an array of different colored gemstones. Also, sapphires may be heat treated with beryllium to achieve many different artificial colors of sapphire gemstones. At one time only the surface of the sapphires were artificially colored, but now the treatments can completely penetrate the entire gemstone. This makes it more difficult to identify artificially colored sapphires. All gemstone treatments must be disclosed by the vendor prior to the sale of a gemstone.

 

**To learn more about gemstone treatments, please refer to my "Gemstone Treatments, Enhancements, & Care" page.

 

Can The Color Of My Minerals Or Gemstones Fade?

 

The colors of some minerals and gemstones can be altered by time or exposure to sunlight or bright display lights. Some may fade, while others may oxidize. Some porous gems, such as Agate, Lapis Lazuli, Pearls, and Turquoise may be treated to stabilize their color. Gemstones that have had their color altered through the various treatments may also fade, change color, or become spotty over time.

 

Minerals & Gemstones That Are Sensitive To Light

 

Upon exposure to different kinds of light many minerals and gemstones can undergo changes in color or transparency. Some may fade, while others can darken. Temporary color changes may also occur. Not all of a given gemstone or mineral will be sensitive to light. Sometimes a certain location/source will be the deciding factor. Also, certain color varieties or individual colors of a mineral or gem will be light sensitive. Other times all of a certain mineral or gem will be light sensitive. If in doubt, be aware that it can occur and take preventative measures to protect the mineral specimen or gemstone from prolonged light exposure. Even if a particular mineral that you have is not listed below, please keep an eye on it if it will be undergoing prolonged light exposure. Some minerals and gems, such as Hiddenite/Green Spodumene and Yellow Phenakite can fade within only one hour of exposure to bright light or sunlight!

 

These minerals, some of their family members, or some of their color varieties have been reported to show some type of sensitivity to light: Agate, Amazonite, Amethyst, Apatite, Aquamarine, Aragonite, Argentite, Barite, Bermanite, Beryl, Bromargyrite, Bustamite, Calcite, Celestite, Chalcopyrite, Chlorargyrite, Chrysoprase, Cinnibar, Citrine, Corderoite, Corundum/Sapphire, Crocoite, Creedite, Cuprite, Diamond, Fluorapatite, Fluorite, Hackmanite, Halite, Hiddenite/Green Spodumene, Inesite, Kunzite/Pink Spodumene, Lapis Lazuli, Marcasite, Microcline, Morganite, Morion Quartz, Opal, Orpiment, Pararealgar, Pearls, Phenakite, Prasiolite/Green Quartz, Proustite, Pyrargyrite, Pyrite, Realgar, Rose Quartz, Scapolite, Silver (Native), Smoky Quartz, Sodalite, Spinel, Stephanite, Terlinguacreekite, Tetrahedrite, Topaz, Tourmaline, Tugtupite, Turquoise, Vanadinite, Vivianite, Wulfenite, and Zircon.  

 

*The gemstones shown at the top of the page are (L to R): Apatite, Kunzite, & Blue Zircon

 



 

**If the images and/or text on any of the web pages do not appear evenly spaced and centered on your screen, which commonly occurs with AOL pages, maximize the individual page's window. That should resolve the problem.

 

 

 

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