Opal

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October Birthstone

While we often think of opal in terms of phenomenal play of color, this gemstone family is full of other unique and appealing members that have their own allure. Gems can be transparent, translucent or opaque and form in almost any color in many locations around the world. Get to know all the varieties of this unique family by looking at our fire opal, dendritic opal, hyalite, Caramel Spice Opal (TM), Morado Opal (TM), along with even more blue, pink and green varieties. With such an endless array, opal truly is the 'Queen of Gemstones'.

Opal Polished
Opal Classification
Common Name Opal
Species Opal
Opal Optical Properties
Transparency Translucent - Opaque
Refractive Index 1.370-1.470
Optic Character NA
Polariscope Reaction Singly Refractive (SR) With ADR, Aggregate (AGG)
Fluorescence SWUV: inert to strong green or yellowish green
LWUV: inert to strong green or yellowish green
Pleochroism None
Opal Characteristic Physical Properties
Hardness 5-6.5
Streak White
Specific Gravity 1.980-2.500 Typical:2.150
Toughness Varies
Luster Vitreous, Resinous
Fracture Conchoidal, Uneven
Cleavage None
Opal Chemistry & Crystallography
Chemical Name hydrated silicon dioxide
Chemical Formula SiO2.nH2O
Crystal System NA
Chemistry Classification Silicate

Opal Colors

  • Bi-color Opal Bi-color
  • Yellow Opal Yellow
  • White Opal White
  • Purple Opal Purple
  • Pink Opal Pink
  • Orange Opal Orange
  • Colorless Opal Colorless
  • Green Opal Green
  • Black Opal Black

Opal Spectra

Opal Spectra
OPAL

Color due to internal structure. A typical spectrum of fire opal showing transmission only in the orange - red area with an abrupt cut off at 585nm

Jewelry Television acknowledges the significant scientific contributions of John S Harris, FGA to the study of gemstone spectra and with deep appreciation to him, acknowledges the use of his images and related notes about gemstones and their spectra in the educational materials on this website.

Alternate Names

Potch, Opal Without Play-Of-Color, Common Opal, Colored Opal, Precious Opal, Opal With Play-Of-Color, Gilson Opal

Countries of Origin

Tanzania, United Republic Of; Afghanistan; Madagascar; Thailand; Pakistan; Unknown; Mali; China; Russian Federation (the); Brazil; Lithuania; Serbia; Nepal; United Kingdom of Great Britain and Northern Ireland (the); United States of America (the); Republic of Kosovo; Japan; Switzerland; India; Canada; Honduras; Mexico; South Africa; Australia; Peru; Ethiopia; Germany; Indonesia

History

Opals are rainbows you can hold in your hands, wear at your neckline, drop from your ears and wrap around your wrists. Opals, with their dancing inner colors, match everything and anything. Red, green, yellow, blue, orange, pink... opals have it all. At their most alluring, opals represent a gathering of elusive rainbows that flash, sparkle and hide in an unending dance. Almost ethereal, opals have a cool inner light that scatters from the heart of each stone - soft splashes of blue, whispers of yellow, occasional pops of pink, green, orange and red. They are spectacular stones with haunting beauty, interior rainbows, and/or fascinating fern-like inclusions. Opals are true masterpieces from Mother Nature.

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Sisk Gemology Reference

Showcasing 200 gemstones in over 1,000 pages and accompanied by more than 2,000 photos, The Sisk Gemology Reference is a must-have in every collector’s library. Each comprehensive, three-volume set features state-of-the-art photography, detailed illustrations, and scientifically precise descriptions to create an entrancing experience for gemstone amateurs and afficionados alike.

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Simulants

Plastic Opal Simulant

Some gems, like opal, are highly coveted, but rare to find, much less in the sizes and quality people dream of owning. Plastic opal simulants offer a budget friendly alternative to natural opal.

Plastic Opal Simulant Opal
Plastic Opal Simulant Classification
Common Name Plastic Opal Simulant
Plastic Opal Simulant Optical Properties
Refractive Index 1.53-1.48
Fluorescence SWUV: Inert to weak chalky white
LWUV: Strong chalky white

Glass Opal Simulant

Some gems, like opal, are highly coveted but rare to find, much less in the sizes and quality people dream of owning. Glass opal simulants offer you the best of both worlds. You get the beauty of a beautiful natural opal, but at a budget-friendly price. This glass simulant recreates the beautiful play-of-color coveted in natural opal.

Glass Opal Simulant Opal
Glass Opal Simulant Classification
Common Name Glass Opal Simulant
Glass Opal Simulant Optical Properties
Refractive Index 1.5-1.52
Fluorescence SWUV: Variable
LWUV: Variable
Glass Opal Simulant Characteristic Physical properties
Specific Gravity 2.41
Inclusions Glass opal simulants contain iridescent flakes of metallic foil that give the illusion of play of color. Sometimes gas bubbles can be seen.

Species/Variety

Ethiopian Opal

Opal with play of color has always been considered one of the most desired gems in the marketplace, earning it the undisputed title as 'Queen of Gemstones'. With the discovery of precious (and stable) opal in Ethiopia's northern Welo District in 2008, coupled with its prolific bounty, this remarkable gem has reclaimed its throne and rules again as one of the most in-demand gemstones in the 21st century.

Ethiopian Opal Opal
Ethiopian Opal Classification
Common Name Ethiopian Opal
Ethiopian Opal Optical Properties
Dispersion Strength: none
Refractive Index 1.45
Tolerance:-0.25
Fluorescence SWUV: Variable
LWUV: Variable
Ethiopian Opal Characteristic Physical properties
Specific Gravity 1.25
Inclusions Ethiopian opal will have play-of-color in various patterns, such as pinfire (small patches or dots), flash (large areas of color), harlequin (brush-strokes of color); flagstone and other unique patterns.

Matrix Opal

Opal in matrix gems consist of precious opal, often cut en cabochon, with an outer layer of its host rock still attached. This stark contrast of glittering translucent opal with earthy rock makes for beautiful, one-of-a-kind pieces.

Matrix Opal Opal
Matrix Opal Classification
Common Name Matrix Opal
Matrix Opal Optical Properties
Dispersion Strength: none
Fluorescence SWUV: Variable
LWUV: Variable
Matrix Opal Characteristic Physical properties
Specific Gravity 1.98
Inclusions Opal in matrix is precious opal mixed throughout a brown ironstone, quartzite, rhyolite or basalt host rock. Stones will have a pock marked appearance with little holes when viewed with a 10X loupe.Andamooka matrix opal will have sheets of color broken up by non-opal material and the edges of color will appear serrated. Andamooka matrix opal is often dyed black and will have black color concentrations that can be seen under magnification. Chips on the stones surface might expose the white inner core. Honduras opal has small flecks of opal in matrix that give it a pinfire appearance and it is lighter than other opal.

Creation Classification

Lab Created

Some gems, like opal, are highly coveted but rare to find, much less in the sizes and quality people dream of owning. Synthetic, or laboratory created jewels, offer you the best of both worlds. You get the beauty of a beloved, rare gemstone, but at a budget friendly price. The term synthetic refers to a man-made material with a natural counterpart. The synthetic crystal replicates the chemical, optical and physical properties of the natural crystal with little or no variation.

Lab Created Opal
Lab Created Classification
Common Name Lab Created
Lab Created Optical Properties
Refractive Index 1.43-1.47
Fluorescence SWUV: Variable
LWUV: Variable
Lab Created Characteristic Physical properties
Specific Gravity 1.97
Inclusions You can see the columnar structure of synthetic opal when viewed from the side.The stones play of color patterns often look like snake skin or chicken wire under magnification. Stones with vivid colors are probably polymer impregnated.

Material Composition

Opal Triplet

Opal triplets combine natural opal with layers of other materials. A thin slice of natural opal is assembled between a base (usually of matrix, plastic, glass or other material) and a colorless top that protects the natural opal. On occasion, the bonding agent may account for the third layer. Opal triplets typically provide a more affordable alternative to natural, solid opal.

Opal Triplet Opal
Opal Triplet Classification
Common Name Opal Triplet
Opal Triplet Optical Properties
Refractive Index 1.47
Opal Triplet Characteristic Physical properties
Inclusions In opal triplets look for assembled nature and glue layer.Look for straight separation planes to distinguish opal triplets from natural opal that contain a potch opal under layer.Stones might have areas of potch or matrix that lack play-of-color. Synthetic opal will have a more uniform play-of-color appearance. The base of the stones are sometimes glued using black cement to give the appearance of a black opal.

Opal Doublet

An opal doublet is an assembled gem that consists of a thin slice of natural opal attached to a second layer of material with a bonding agent. The types of materials used for opal doublets vary considerably but may include ironstone, sandstone, black plastic or quartz. Opal doublets often provide a more affordable alternative to solid opals and are often used today for mass-produced jewelry.

Opal Doublet Opal
Opal Doublet Classification
Common Name Opal Doublet
Opal Doublet Optical Properties
Refractive Index 1.45
Tolerance:-0.25
Opal Doublet Characteristic Physical properties
Inclusions Look for assembled nature and glue layer in opal doublets. Look for straight separation planes to distinguish opal doublets from natural opal that contain a potch opal under layer. These stones might have areas of potch or matrix that lack play-of-color. Synthetic opal will have a more uniform play-of-color appearance. Stones are sometimes glued using black cement to give the appearance of a black opal.

Mosaic Opal Triplet

As an affordable alternative to larger sized solid opals, mosaic opal triplets provide an affordable, and stylish, substitute. They are created by assembling a montage of small, thin opal slices and adhering them to a solid base material, which may be natural or man-made. The base material, often dark in color, provides a dramatic backdrop to the overall appearance of the triplet.

Mosaic Opal Triplet Opal
Mosaic Opal Triplet Classification
Common Name Mosaic Opal Triplet
Mosaic Opal Triplet Optical Properties
Refractive Index 1.47
Mosaic Opal Triplet Characteristic Physical properties
Inclusions Look for assembled nature and glue layer of a mosaic opal triplet. Stones are made up of small irregular shaped pieces of opal glued on a base.Stones have the appearance of a mosaic tile.
Tim Matthews

Author

Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.