Buy Gems: Natural Loose Gemstones HomeNew ArrivalsAbout UsHelpContactSite MapBuyers GuideAccountsCart Open GemSelect Shopping Cart
Gem Info :: Refractive Index
Back Back Forward
Loose Gemstones Direct from the Source
Items: 0 | Total: $0.00
Loose Gemstones Direct from the Source  
Refractive Index Chart

Refractive index, or RI as it is often abbreviated, is one of the most important signatures of a gemstone. Measuring refractive index is one of the first steps in identifying a gemstone, though some gemstones have similar refractive indices and additional tests are required for a definitive identification.

RI is the ratio of the velocity of light in air to the velocity of light through a transparent material. If light passes from air into a transparent material at an angle of incidence other than a 90 degree angle, it is deflected at a different angle (the coincident angle) according to the RI. Gemstones with higher RI are generally more brilliant than those with low RI, because more light is returned back out the top or crown of the stone, instead of passing through the bottom or pavilion. Diamond has an RI of about 2.4; quartz, about 1.54-1.55. The RI of most gemstones is easily measured using a simple optical instrument known as a refractometer.

Some gemstones are singly refractive: they have only one refractive index. Other gemstones -- in fact, most -- are doubly refractive: they have two different refractive indices. When a beam of light enters a doubly refractive gem, it is split into two beams, each travelling at a different speed and on a different path through the crystal. Birefringence is a measurement of the difference between the two refractive indices in gems that are doubly refractive, and it ranges from a low of .003 to a high of .287. Very few gemstones are singly refractive; in fact, the only well-known gems with that property are diamond, spinel and garnet.

The following chart lists the refractive indices for about 60 varieties of gemstones, sorted in descending order.

 

Buy Diamond from GemSelect Diamond Natural Emerald Gemstones Emerald
2.417 - 2.419 1.565 - 1.602
 
Sphene from GemSelect Sphene Buy Beryl Online Beryl
1.691 - 1.700 1.565 - 1.602
 
Natural Zircon Zircon Aquamarine from GemSelect Aquamarine
1.81 - 2.02 1.564 - 1.596
 
Natural Spessartite Garnet from GemSelect Spessartite Garnet Buy Morganite Online Morganite
1.79 - 1.82 1.562-1.602
 
Buy Almandine Garnet Online Almandine Garnet Ametrine from GemSelect Ametrine
1.77 - 1.82 1.544 - 1.553
 
Buy Natural Sapphire Sapphire Buy Quartz Gems Online Quartz
1.762 - 1.788 1.544 - 1.553
 
Ruby at GemSelect Ruby Natural Citrine from GemSelect Citrine
1.762 - 1.778 1.544 - 1.553
 
Buy Chrysoberyl Gemstones Chrysoberyl Natural Aventurine at GemSelect Aventurine
1.746 - 1.763 1.544 - 1.553
 
Garnet Gems from GemSelect Grossularite Garnet Buy Natural Amethyst Online Amethyst
1.734 - 1.759 1.544 - 1.553
 
Natural Tsavorite Garnet Tsavorite Garnet
Natural Rutile Quartz Rutile Quartz
1.734 - 1.759 1.544 - 1.553
 
Natural Pyrope Garnet Pyrope Garnet
Onyx gems Onyx
1.720 - 1.756 1.544 - 1.553
 
Garnet Gems from GemSelect Garnet
Buy Rose Quartz Online Rose Quartz
1.720 - 1.756 1.544 - 1.553
 
Buy Rhodolite Garnet from GemSelect Rhodolite Garnet
Natural Smoky Quartz at GemSelect Smoky Quartz
1.72 - 1.76 1.544 - 1.533
 
Natural Spinel Gems from GemSelect Spinel
Buy Iolite Online Iolite
1.712 - 1.762 1.542 - 1.578
 
Kyanite Gems at GemSelect Kyanite
Tigers Eye at GemSelect Tiger's Eye
1.710 - 1.734 1.534 - 1.540
 
Natural Tanzanite Gems from GemSelect Tanzanite
Natural Jaspwer from GemSelect Jasper
1.691 - 1.700 1.54
 
Ruby Zoisite at GemSelect Ruby-Zoisite
Buy Agate at GemSelect Agate
1.691 - 1.700 1.53 - 1.54
 
Natural Chrome Diopside Chrome Diopside
Natural Chalcedony Chalcedony
1.664 - 1.730 1.53 - 1.54
 
Spodumene Gemstones Spodumene
Buy Andesine Online Andesine
1.660 - 1.681 1.522 - 1.530
 
Natural Kunzite Gems from GemSelect Kunzite
Amazonite Gems Online Amazonite
1.660 - 1.681 1.522 - 1.530
 
Hiddenite from GemSelect Hiddenite
Pearls at GemSelect Pearl
1.660 - 1.681 1.52 - 1.69
 
Natural Jade Jade
Buy Orthoclase from GemSelect Orthoclase
1.652 - 1.688 1.518 - 1.526
 
Buy Peridot from GemSelect Peridot
Buy Moonstone Online Moonstone
1.650 - 1.703 1.518 - 1.526
 
Buy Apatite Online Apatite
Natural Lapis Lazuli Lapis Lazuli
1.628 - 1.649 1.5
 
Natural Andalusite Andalusite
Buy Fluorite Online Fluorite
1.627 - 1.649 1.434
 
Natural Tourmaline from GemSelect Tourmaline
Natural Opal Opal
1.614 - 1.666 1.37 - 1.52
 
Buy Prehnite Online Prehnite
Buy Fire Opal Online Fire Opal
1.611-1.669 1.37 - 1.52
 
Turquoise from GemSelect Turquoise
Moss Opal at GemSelect Moss Opal
1.610 - 1.650 1.37 - 1.52
 
Buy Topaz Online from GemSelect Topaz
   
1.609 - 1.643  
Help
• Shipping
• Payment
• Return Policy
• Security and Privacy
• Guarantee
Gemstone Information
• GemSelect Newsletters
• Sapphire
• Semi-Precious Stones
• Rare Spinel
• Calibrated Gemstone Chart
• Lapis Lazuli
• Emerald Information
• Zircon and Zirconology
• Blue Sapphire
• Gem Hardness and Durability
• Andesine Labradorite
• Star Moonstone
• Apatite Information
• Red Spinel
• Iolite Information
• Ceylon Sapphire
• Tsavorite Garnet
• Aquamarine Information
• Spessartite Garnet
• Rhodolite Garnet
• Round Tourmaline
• Imperial Topaz
• Watermelon Tourmaline
• Pink Tourmaline
• Bi-Color Tourmaline
• Huge Gems
• Tanzanite Information
• Concave Cuts
Pay Gemstones with Credit Card Pay Gems with PayPal Pay Gem Stones with Visa Delta Ship Gemstones with USPS Secure Payment Fair Gemstone Trade supported by Square Trade
Ship Gemstones securely with FedEx
GO!