kristin
12-02-2005, 12:34 PM
Color-
Color is typically the most important value-setting factor for gemstones. All gems have a preferred color, or range of preferred colors. The more the color varies from this range the less valuable the stone.
Color is composed of 3 dimensions: hue, tone, and saturation.
Hue- is the impression of the color usually noticed immediately, such as red, blue or green.
Tone- is the degree of lightness or darkness of the stone.
Saturation- is the degree of purity of a hue.
Cut -
Cut refers to the shape or design of a stone, arrangement of facets and the precision of the stone's proportions and finish.
Clarity-
A gemstone's clarity is directly related to it's rarity. Clarity refers to a gem's relative freedom from clarity characteristics. Clarity characteristics are inclusions (which are inside the stone) and blemishes (which are on the surface of the stone). The fewer clarity characteristics, the more rare the stone.
Each variety of gemstone has it's own clarity standards. For example Aquamarine is virtually free of inclusions while Emerald almost always contains inclusions. For this reason GIA's grading system divided transparent colored stones into 3 clarity types. Type I, Type II, and Type III. Each type is further divided into 5 grading descriptions. Eye clean, slightly included, moderately included, heavily included, and severely included.This allows gems to be more evenly evaluated.
Type I gemstones are often virtually free of clarity characteristics.
Common examples of type I gemstones are Aquamarine, Green Tourmaline, Tanzanite, Blue Topaz and Blue Zircon.
Eye clean- appears clean to unaided eye
Slightly Included- minute inclusions difficult to see with the unaided eye.
Moderately Included- minor inclusions somewhat easy to see with the unaided eye.
Heavily Included- prominent inclusions that have anegative effect on appearance or durability.
Severly Included- prominent inclusions that have a severe effect on appearance, durability, or both.
Type II gemstones normally contain clarity characteristics.
Common examples of type II gemstones are Alexandrite, Amethyst, Citrine, Peridot, Ruby, Garnets, Sapphire (all colors), and Spinel (all colors).
Eye clean- appears clean to unaided eye
Slightly Included- minor inclusions somewhat easy to see with the unaided eye.
Moderately Included- noticeable inclusions apparent to the unaided eye.
Heavily Included- prominent inclusions that have anegative effect on appearance or durability.
Severly Included- prominent inclusions that have a severe effect on appearance, durability, or both.
Type III gemstones almost always contain clarity characteristics.
Common examples of type III gemstones are Emerald and Watermelon Tourmaline.
Eye clean- appears clean to unaided eye
Slightly Included- noticeable inclusions apparent to the unaided eye.
Moderately Included- obvious inclusions very apparent to the unaided eye.
Heavily Included- prominent inclusions that have anegative effect on appearance or durability.
Severly Included- prominent inclusions that have a severe effect on appearance, durability, or both.
Carat Weight-
Gemstones, like Diamonds are measured by carats. The metric carat can be divided into smaller units called points. Points to a carat and like pennies to a dollar. Up to a certain point the larger a stone is the more rare it is and the higher the value. 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.
Color is typically the most important value-setting factor for gemstones. All gems have a preferred color, or range of preferred colors. The more the color varies from this range the less valuable the stone.
Color is composed of 3 dimensions: hue, tone, and saturation.
Hue- is the impression of the color usually noticed immediately, such as red, blue or green.
Tone- is the degree of lightness or darkness of the stone.
Saturation- is the degree of purity of a hue.
Cut -
Cut refers to the shape or design of a stone, arrangement of facets and the precision of the stone's proportions and finish.
Clarity-
A gemstone's clarity is directly related to it's rarity. Clarity refers to a gem's relative freedom from clarity characteristics. Clarity characteristics are inclusions (which are inside the stone) and blemishes (which are on the surface of the stone). The fewer clarity characteristics, the more rare the stone.
Each variety of gemstone has it's own clarity standards. For example Aquamarine is virtually free of inclusions while Emerald almost always contains inclusions. For this reason GIA's grading system divided transparent colored stones into 3 clarity types. Type I, Type II, and Type III. Each type is further divided into 5 grading descriptions. Eye clean, slightly included, moderately included, heavily included, and severely included.This allows gems to be more evenly evaluated.
Type I gemstones are often virtually free of clarity characteristics.
Common examples of type I gemstones are Aquamarine, Green Tourmaline, Tanzanite, Blue Topaz and Blue Zircon.
Eye clean- appears clean to unaided eye
Slightly Included- minute inclusions difficult to see with the unaided eye.
Moderately Included- minor inclusions somewhat easy to see with the unaided eye.
Heavily Included- prominent inclusions that have anegative effect on appearance or durability.
Severly Included- prominent inclusions that have a severe effect on appearance, durability, or both.
Type II gemstones normally contain clarity characteristics.
Common examples of type II gemstones are Alexandrite, Amethyst, Citrine, Peridot, Ruby, Garnets, Sapphire (all colors), and Spinel (all colors).
Eye clean- appears clean to unaided eye
Slightly Included- minor inclusions somewhat easy to see with the unaided eye.
Moderately Included- noticeable inclusions apparent to the unaided eye.
Heavily Included- prominent inclusions that have anegative effect on appearance or durability.
Severly Included- prominent inclusions that have a severe effect on appearance, durability, or both.
Type III gemstones almost always contain clarity characteristics.
Common examples of type III gemstones are Emerald and Watermelon Tourmaline.
Eye clean- appears clean to unaided eye
Slightly Included- noticeable inclusions apparent to the unaided eye.
Moderately Included- obvious inclusions very apparent to the unaided eye.
Heavily Included- prominent inclusions that have anegative effect on appearance or durability.
Severly Included- prominent inclusions that have a severe effect on appearance, durability, or both.
Carat Weight-
Gemstones, like Diamonds are measured by carats. The metric carat can be divided into smaller units called points. Points to a carat and like pennies to a dollar. Up to a certain point the larger a stone is the more rare it is and the higher the value. 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.