Global Gemology - Rare Gems & Jewels
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DIAMOND

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A beautiful marquise diamond centers this white gold and diamond bypass ring, by A. Altier Jewelers
A marquise brilliant cut diamond ring
Species:  Diamond
Mohs Hardness:  10 out of 10
Color:  Diamonds on GIA's D to Z color scale range from colorless to pale yellow, brown or gray.  (Diamonds occur in nearly all colors and are known as "fancy colored diamonds".  i.e. Fancy yellow, brown, pink, blue, green, etc.)
RI:  2.42
Birefringence:  None
SR/DR/AGG:  SR
Spectrum:  Almost all near-colorless to light yellow diamonds show the “cape” line at 415.5 nm, along with weaker lines at 435 nm, 451 nm, 463 nm, and 478 nm. (Cooling the diamond with liquid nitrogen helps make its spectrum more visible.)
Fluorescence:  Typically inert or weak to strong blue, but might fluoresce any color under LW and SW.  LW response is usually stronger than, or equal to, SW. 
SG:  3.52 (+/-0.10)
Routine Treatments:  None
Additional Enhancements:  Laser drilling, fracture filling, HPHT (high pressure, high temperature), irradiation
SHOP DIAMOND JEWELRY

Diamond Facts

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Diamond
Close-up shot of a round brilliant cut diamond

​​Diamonds in the finest qualities command the highest prices per carat of all gems.
​
Diamonds are composed of 99.95% carbon.  The other 0.05% can include 1 or more trace elements that can affect the color of the diamond crystal.
 
Diamond is a 10 out of 10 on the Mohs scale of hardness.  Their resistance to scratching, in addition to their beauty, is another reason why they’re so popular in jewelry.​
​
Diamonds form under conditions of extremely high temperature and pressure that exist over 100 miles beneath the earth's surface.
 
The value of a diamond is determined by "The 4 Cs":  cut, color, clarity & carat weight.  What shape / how well is the diamond cut?  Is the diamond colorless or does it have a faint yellow tinge?  Does the diamond have any noticeable inclusions with the naked eye?  How much does the diamond weigh?
 
Diamonds are weighed in carats.  There are 100 points in 1 carat (60 points = 0.60 carat) and 5 carats in 1 gram.
 
Diamond is an April birthstone, is the traditional engagement gemstone, and is the 60th & 75th wedding anniversary gemstone.

HISTORY OF DIAMOND CUTS

Cut

THE 4 "C"s
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Types of diamond shapes / cutting styles
Photo courtesy of James & Company
What shape and cutting style is the diamond?  Below is a list of commonly seen diamond shapes/cutting styles:

• Marquise Brilliant Cut
• Radiant Cut
• Trillion Cut
• Baguette
• Oval Brilliant Cut
• Emerald Cut
• Princess Cut
• Round Brilliant Cut

• Asscher Cut
• Cushion Brilliant Cut
• Tapered Baguette
• Heart Shape Brilliant Cut
• Pear Shape Brilliant Cut
​(& more)


Color

THE 4 "C"s
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Examples of GIA's D to Z diamond color grades
Photo courtesy of GIA

GIA has developed a universally-accepted color grading system for colorless diamonds.  This scale ranges from D to Z, with D being completely absent of any body color and Z being a light yellow diamond.  Diamonds that are more yellow than Z color would be graded using the fancy color grading system.

GIA's D to Z diamond color grade scale

Fancy color diamonds can occur in nearly all colors including yellow, brown, gray, black, blue, pink, orange, green, and red.  These colored diamonds are graded using GIA's fancy color grading system.

For colored diamonds, the color strength grades are:


• Faint
• ​Very Light
• Light
• Fancy Light
• Fancy
• Fancy Intense
• Fancy Vivid
• Fancy Vivid Dark
• Fancy Vivid Deep

Clarity

THE 4 "C"s
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GIA's diamond clarity grading scale

​Since diamonds form deep beneath the earth's surface under extreme conditions, they will often contain unique clarity characteristics.  These characteristics range from included mineral crystals to cavities or twinning wisps.

Here is a brief description of GIA's Clarity Scale:

​
Flawless (FL)
No inclusions or blemishes visible under 10x magnification.


Internally Flawless (IF)
No inclusions, only blemishes visible under 10x magnification.


Very, Very Slightly Included (VVS1 to VVS2)
Minute inclusions, difficult to notice, visible under 10x magnification.


Very Slightly Included (VS1 to VS2)
Minor inclusions, ranging from difficult to somewhat easy to notice, under 10x magnification.


Slightly Included (SI1 to SI2)
Noticeable inclusions under 10x magnification.


Included (I1 to I3)
Obvious inclusions under 10x magnification that can affect appearance and/or durability.

Carat Weight

THE 4 "C"s
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​Diamond weights are measures in carats.  There are 100 points in a carat and 5 carats in a gram (40 points = 0.40 carat).

1/4 carat = 0.25 ct.
1/2 carat = 0.50 ct.
3/4 carat = 0.75 ct.
1 carat = 1.00 ct.

Diamond Cut Grade

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Diamond proportions illustration

The quality of a diamond's cut directly affects its brilliance.  The Gemological Institute of America (GIA) has developed a Diamond Cut Grade Scale that grades a round brilliant cut diamond's overall proportions.  It's based on the assessment of the following 7 components:

• Brightness
• Fire
• Scintillation
• Weight Ratio
• Durability
• Polish
• Symmetry

GIA Cut Grading Scale

The following measurements are factored into the grading of the overall cut:

• Table Size
• Total Depth Percentage
• Crown Height
• Crown Angle
• Pavilion Depth
• Pavilion Angle
• Girdle Thickness
• Star Facet Length
• Lower Girdle Facet Length
• Culet

** GIA's Diamond Cut Grade Scale applies to round brilliant cut diamonds only. **

GIA diamond cut grade factors

Diamond Gallery

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​All photos courtesy of Scott Papper, GIA GG, AJP, CMA (NAJA)

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Lab Grown DiamondS & Diamond Treatments

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LAB CREATED DIAMONDS
DIAMOND TREATMENTS
  • HOME
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  • SHOP
  • SERVICES
    • APPRAISALS
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  • GEMOLOGY
    • GEM ENCYCLOPEDIA
    • THE ART OF GEMOLOGY
  • JEWELRY EDUCATION
    • DIAMOND FACTS
    • JEWELER DIRECTORY
    • JEWELRY PERIODS
    • POCKET WATCHES
    • NATIVE AMERICAN JEWELRY
  • GLOSSARY