Opal

saf-ahyuh r
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

  • Purple Opal Purple
  • Multi-color Opal Multi-color
  • Gray Opal Gray
  • Brown Opal Brown
  • Blue Opal Blue
  • Orange Opal Orange
  • Pink Opal Pink
  • Green Opal Green
  • Red Opal Red
  • White Opal White
  • Black Opal Black

Opal Spectra

Opal Spectra
OPAL

Color due to internal structure. Like most fire opals there is very little transmission in the violet blue side of the visible spectrum. In the lighter colored stones as here, absorption sets in about 540nm. but in the darker specimens only red and orange may be transmitted.

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

Myanmar; Cameroon; Papua New Guinea; Angola; Cambodia; Malaysia; Kazakhstan; Paraguay; Portugal; Iceland; Oman; Greece; Austria; Mongolia; Korea (the Republic of); Morocco; Unknown; Mali; Panama; Brazil; Algeria; Chile; Colombia; Ecuador; Argentina; United States of America (the); Hungary; Republic of Kosovo; Japan; Ukraine; Bolivia (Plurinational State of); India; New Zealand; Canada; Vanuatu; Turkey; Belgium; Namibia; Finland; Honduras; Italy; South Africa; Antarctica; Georgia; Peru; Venezuela (Bolivarian Republic of); Ethiopia; Germany; Tanzania, United Republic Of; Afghanistan; Fiji; Viet Nam; Czechia; Egypt; Somalia; Madagascar; Marshall Islands (the); Thailand; Libya; Costa Rica; Saudi Arabia; Sweden; Pakistan; China; Russian Federation (the); Poland; Slovakia; Bulgaria; France; Jordan; Lithuania; Serbia; United Kingdom of Great Britain and Northern Ireland (the); Romania; Togo; Sri Lanka; Rwanda; Uzbekistan; Kenya; Switzerland; Spain; Cuba; Mauritania; Saint Lucia; Norway; Denmark; Mexico; Zimbabwe; Israel; Australia; Greenland; 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 1.48-1.53
Fluorescence SWUV: Inert to weak chalky white
LWUV: Strong chalky white
Plastic Opal Simulant Characteristic Physical properties
Specific Gravity 1.20
Toughness Poor
Inclusions multi-color polygonal patches

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

Hyalite Opal

Hyalite opal is known to come from Australia, Brazil, Mexico, Russia, South Africa and the U.S. It is named from the Greek word meaning ‘glass stone’ due to its glass-like appearance. It is colorless and does not display play-of-color and commonly forms as botryoidal aggregates.

Hyalite Opal Opal
Hyalite Opal Classification
Common Name Hyalite Opal
Hyalite Opal Characteristic Physical properties
Specific Gravity 2.0
Toughness Fair
Stability Poor

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.

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
CCF Reaction Brown stones might appear red
Ethiopian Opal Characteristic Physical properties
Specific Gravity 1.35
Toughness Fair
Inclusions Many will have tiny brown inclusions and some have rough filled tubes. 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.
Stability Fair

Prase Opal

Prase Opal is the yellowish to bluish green variety of common opal. The material obtains its color from Nickel. It is most often found in Kosovo, Iyobo Mountain mine in Tanzania and in California in the United States.

Prase Opal Opal
Prase Opal Classification
Common Name Prase Opal
Prase Opal Optical Properties
Refractive Index Typical 1.455
Fluorescence None
CCF Reaction None
Prase Opal Characteristic Physical properties
Specific Gravity 2.09
Toughness Fair
Inclusions Goethite
Stability Good

Fire Opal

Fire Opal is a variety of transparent to translucent red, orange to brown or yellow opal. It typically does not display play-of-color phenomena but occasionally fine examples with play-of-color will occur. Fire opal is best known from North, Central and South American but it has multiple sources around the world.

Fire Opal Opal
Fire Opal Classification
Common Name Fire Opal
Fire Opal Optical Properties
Fluorescence Might be phosphorescent
Fire Opal Characteristic Physical properties
Specific Gravity 1.97
Toughness Varies
Inclusions Fire opal might have a cloudy appearance, show color zoning and have mineral or fluid inclusions
Stability Fair

Green Opal

Green opal is the variety of green common opal that derives its color from iron. It is different from Prase opal that gets its color from Nickel. Green opal comes from Australia, Madagascar, Mali, Peru, Serbia and South Africa.

Green Opal Opal
Green Opal Classification
Common Name Green Opal
Green Opal Optical Properties
Fluorescence Might be phosphorescent
Green Opal Characteristic Physical properties
Specific Gravity 1.98
Toughness Fair

Black Opal

Black Opal was discovered in 1902 and is the rarest and most valuable variety of opal. Any opal material that displays play-of-color against a dark body tone can be described as Black Opal. Lightning Ridge in Australia is the best-known location, but it is also known to come from Mintabie, Australia, Java, Virgin Valley, Nevada and Wollo, Ethiopia.

Black Opal Opal
Black Opal Classification
Common Name Black Opal
Black Opal Optical Properties
Fluorescence Might be phosphorescent
Black Opal Characteristic Physical properties
Specific Gravity 2.07
Toughness Fair
Inclusions Might contain matrix areas that do not display play-of-color
Stability Poor

Boulder Opal

Boulder Opal, also known as Queensland Opal, comes from Queensland, Australia. The material contains precious opal in an ironstone or sandstone matrix.

Boulder Opal Opal
Boulder Opal Classification
Common Name Boulder Opal
Boulder Opal Optical Properties
Refractive Index 1.450
Boulder Opal Characteristic Physical properties
Specific Gravity 1.980
Toughness Good
Inclusions Precious opal in ironstone or sandstone matrix
Stability Poor

Leopard Opal

Leopard Opal is precious opal with play-of-color sprinkled throughout Vesicular Basalt rock. The colorful opal is striking against the black stone matrix. It is only found in Zimapán, Hidalgo State, Mexico.

Leopard Opal Opal
Leopard Opal Classification
Common Name Leopard Opal
Leopard Opal Optical Properties
Refractive Index 1.460
Leopard Opal Characteristic Physical properties
Toughness Good
Inclusions Precious opal in basalt matrix
Stability Poor

Honduran Opal

Honduran Opal is precious opal embedded in grayish or black basalt matrix. Due to the porous structure of the matrix, finished gemstones are often given a quick, hot resin bath and then scrubbed and cleaned. The resin acts as a barrier and helps to prevent the gems from absorbing other substances.

Honduran Opal Opal
Honduran Opal Classification
Common Name Honduran Opal
Honduran Opal Optical Properties
Refractive Index 1.45
Honduran Opal Characteristic Physical properties
Toughness Good
Inclusions Precious opal in basalt matrix
Stability Poor

Contra Luz Opal

Contra Luz Opal will show play-of-color when light from behind. Specimens come from Queretaro, Mexico and Opal Butte, Oregon in the United States of America.

Contra Luz Opal Opal
Contra Luz Opal Classification
Common Name Contra Luz Opal
Contra Luz Opal Optical Properties
Refractive Index 1.45
Contra Luz Opal Characteristic Physical properties
Toughness Good
Stability Poor

Girasol Opal

The term girasol opal applies to Fire Opal that displays play-of-color.

Girasol Opal Opal
Girasol Opal Classification
Common Name Girasol Opal
Girasol Opal Optical Properties
Fluorescence Might be phosphorescent
Girasol Opal Characteristic Physical properties
Specific Gravity 1.97
Toughness Varies
Stability Poor

Yowah Nut

Yowah Nut is a variety of Boulder Opal that derives its name from a locality in the Australian Outback. The nodules are about walnut size and will have colorful veins running throughout.

Yowah Nut Opal
Yowah Nut Classification
Common Name Yowah Nut
Yowah Nut Optical Properties
Refractive Index 1.45
Yowah Nut Characteristic Physical properties
Toughness Good
Inclusions Precious opal in ironstone or sandstone matrix
Stability Poor

Mali Opal

Mali opal was first discovered in 2007 but it was not seen in the gemstone market until 2011. The stones get their color from iron. These opals were formed long ago near the Saharan desert, which was once the site of ancient seas. Production of rough material is very low. Only 50 carats of gemstones will be faceted from every 100 grams of rough material.

Mali Opal Opal
Mali Opal Classification
Common Name Mali Opal
Mali Opal Characteristic Physical properties
Toughness Fair
Inclusions Flow structure, oily appearance,anatase
Stability Poor

Blue Opal

The best-known locations of blue opal come from Peru, Madagascar, Oregon, Arizona and Indonesia. The material ranges from semitranslucent to opaque. Only 10% of the material from Arizona show play-of-color. The Peruvian and Indonesian material gets its color from copper inclusions. The Oregon material gets its color from an optical phenomenon known as Rayleigh scattering.

Blue Opal Opal
Blue Opal Classification
Common Name Blue Opal
Blue Opal Optical Properties
Refractive Index 1.45
Blue Opal Characteristic Physical properties
Specific Gravity 2.13
Toughness Fair
Inclusions Oregon material milky, might show iron staining;
Stability Poor

Caramel Spice Opal™

Caramel Spice Opal™ is reported to come from Ojuelos de Jalisco, Mexico. It is easily distinguished by its rare, unique swirling patterns of brown, tan and white hues. Skilled cutters must carefully study each piece of rough before cutting to determine how to best display its swirl patterns. It has a mohs hardness of 6.

Caramel Spice Opal™ Opal
Caramel Spice Opal™ Classification
Common Name Caramel Spice Opal™
Caramel Spice Opal™ Characteristic Physical properties
Toughness Fair
Stability Poor

Morado Opal®

Morado Opal® is named from the Spanish word for “purple”. The material comes from a remote mining region located along the famous El Camino Real de Tierra Adentro National Historic Trail. The stones get their purple color from fluorite inclusions and are mottled with patches of white. Due to the intergrowth with quartz the stones have a Mohs hardness of 6.

Morado Opal® Opal
Morado Opal® Classification
Common Name Morado Opal®
Morado Opal® Characteristic Physical properties
Toughness Fair
Stability Poor

Pink Opal

Pink opal is found in Peru and Mexico. It is translucent to opaque and comes in brownish pink to pure pink. Pink opal is a combination of opal grains in chalcedony and cristobalite. The chalcedony makes the material slightly more durable and it typically has a Mohs hardness of 5-5.5 but can be up to 6. Peruvian pink opal is colored by manganese. Recent reports attribute the color of pink opal to Palygorskite inclusions and some organic materials.

Pink Opal Opal
Pink Opal Classification
Common Name Pink Opal
Pink Opal Characteristic Physical properties
Specific Gravity 1.98
Toughness Good
Stability Good

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.

Enhancement

Andamooka Matrix

Andamooka Matrix Opal is material from Andamooka, Australia that has been sugar or acid treated. Before treatment the material shows little play-of-color.

Andamooka Matrix Opal
Andamooka Matrix Classification
Common Name Andamooka Matrix
Andamooka Matrix Characteristic Physical properties
Specific Gravity 1.98
Toughness Fair
Inclusions Black carbon particles

Sugar Treated Opal

Sugar-acid treated opal has been submerged in heated sugar or honey solution for several hours to a couple of days. The opal is then submerged in sulfuric acid. The sugar becomes oxidized by the acid and creates carbon particles in the stone.

Sugar Treated Opal Opal
Sugar Treated Opal Classification
Common Name Sugar Treated Opal
Sugar Treated Opal Characteristic Physical properties
Specific Gravity 1.98
Toughness Fair
Inclusions Black carbon particles, chips might reveal white core
Stability Poor

Smoke Treated Opal

Smoked treated stones are wrapped in aluminum foil and then exposed to smoke. The carbon from the smoke will permeate the stone and give a black or brown body color.

Smoke Treated Opal Opal
Smoke Treated Opal Classification
Common Name Smoke Treated Opal
Smoke Treated Opal Characteristic Physical properties
Specific Gravity 1.98
Toughness Fair
Inclusions Black carbon particles, chips might reveal white core
Stability Poor

Dyed Ethiopian Opal

The hydrophane nature of Ethiopian opal allows the material take on dye. This property allows man to create vibrant red, blue, purple, pink or green opals.

Dyed Ethiopian Opal Opal
Dyed Ethiopian Opal Classification
Common Name Dyed Ethiopian Opal
Dyed Ethiopian Opal Characteristic Physical properties
Specific Gravity 1.35
Toughness Fair
Inclusions Uneven color concentrations
Stability Poor
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.