Part-3 Types Of Opals

OPAL TYPES

It is important to know the different types of opal in order to determine the value, quality and the price. There are three distinct types of opals we will learn about: natural opals, composite or enhanced opals and man-made or synthetic opals. The four natural types of opal found are Black opal, Boulder opal, Crystal opal and White opal.

 

TYPES OF NATURAL OPAL

Natural opal is opal which has not been treated or enhanced in any way other than by cutting and polishing. There are three types of natural opal, with varieties described by the two characteristics of body tone and transparency.

    • Natural Opal Type 1 – is opal presented in one piece in its natural state apart from cutting or polishing, and is of substantially homogenous chemical composition. (See figure 3A).
    • Natural Opal Type 2 – is opal presented in one piece where the opal is naturally attached to the host rock in which it was formed and the host rock is of a different chemical composition. This opal is commonly known as boulder opal. (See figure 3B).
    • Natural Opal Type 3 – is opal presented in one piece where the opal is intimately diffused as infillings of pores or holes or between grains of the host rock in which it was formed. This opal is commonly known as matrix opal. (See figure 3C).
 
 
 
A. Natural opal type 1 (All opal)

3A. Natural opal type 1 (All opal)

 
B. Natural opal type 2 (Boulder opal)

3B. Natural opal type 2 (Boulder opal)

 
C. Natural opal type 3 (Matrix opal)

3C. Natural opal type 3 (Matrix opal)

Black Opal

The queen of gems, black opal is the most popular, widely known opal coming from the town famous for its rich, rare and highly valuable opals, Lightning Ridge.

black opal 17-0
    • The opal forms in Iron Oxide called “potch” which can be black or grey.The potch is a non-precious form of opal exhibiting no play of colour. This is where the name Black opal comes from but an opal such as this with no colour is worth very little. The rarest black opals are known and loved for their vibrant colours often with all the colours of the rainbow and the colour is generally found as a colour bar (or bars) of various colours.
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    • Black opal and Boulder opal are the rarest of all opals found, amounting to only 10% of all opal mined. When black and boulder opal are cut the yield is only 5% which means a loss factor of 95%. In comparison to white opal which has a 50% loss factor you can see how this adds to the value of black opal.

Boulder Opal

Found only in Queensland, Boulder opal (along with black opal) is enjoyed around the world as the rarest and most valuable of all opal. It forms in the cracks and crevices of the ironstone country of southwest Queensland.

boulder opal 4new
    • The opal first flowed through the cracks of the boulders in liquid form thousands of years ago. With the passing of centuries the liquid material formed into solid opal with opal cutters now cutting these pieces into magnificent gems with the natural rock left on the back. Due to the dark backing provided by the ironstone, boulder opals generally have a dark body tone which leads to a vibrancy of colour similar to that found in black opals. Boulder opal generally is left in its individual shape and size it is found in, in comparison to the normal round and oval opals to highlight their individual beauty and to avoid unnecessary colour wastage.
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  • With all opal mines slowly running out Boulder Opal is the only opal that has been estimated to run out within the next 5 to 10 years. The reasons for this are because of native land titles in the Queensland Area and the increased damages being caused to the environment in order to mine Boulder Opal. It is estimated that for every 50 tonnes of dirt removed when mining boulder opal only one carat of fine Boulder opal can be found. Because of environmental concerns the government now requires the miners to rehabilitate the area which is proving to be a very expensive process. However it’s not all bad news because these things together with limited supply of boulder opal are actually increasing the value by 25 % every year for at least 10 years in a row so needless to say Boulder opal makes a sound long term investment.

Matrix Opal

Like boulder opal, matrix opal contains precious opal combined with its host rock. In matrix opal, however, the precious opal fills holes or pores between the host rock’s grains, creating a more even play-of-color throughout the stone instead of in distinct sections.

Matrix opal comes from Mexico, Honduras, and Australia. In Australia, Andamooka matrix opal is porous, so it’s easily (and often) chemically treated to improve its color. Honduras produces primarily matrix opal and their opaque variety typically has a dark host rock speckled with vibrant opal. 

dendritic opal pendant

Dendritic Opal

Also called “moss opal,” dendritic opal is a white or yellow-brown type of common opal characterized by green or brown moss-like (dendritic) inclusions. These inclusions, often manganese or iron, form unique patterns, including those reminiscent of a forest landscape seen in “landscape opals.”

Dendritic opals can be nearly 30 percent water, which classifies them as “soft gems.” Most of these opals come from Australia, Mexico, or the USA, but you can also find them throughout Central America, Asia, and Russia. 

opalized wood

Opalized Wood

Opalized wood is a type of petrified wood containing opal. Petrified wood is fossilized timber or vegetation where part of the plant has been replaced by stone, in this case, opal! 

These earthly beauties form when silica water preserves buried wood tissues. Where does this natural phenomenon happen? Opalized wood commonly forms in forests covered in ashfall. Prominent deposits are in the USA, Indonesia, Russia, Mexico, and Brazil.

Moving from combinations formed naturally, let’s look next at how humans combine opals with other materials.

Crystal Opal

Crystal Opal also known as Light opal, is the only opal formed from pure hydrated silica which means it is transparent.

crystal_opal
    • Crystal opal is quite common, representing approximately 30% of opals mined and is found in Coober Pedy in South Australia. The translucence of a crystal opal often gives it a greater clarity and vibrancy of colour than opaque. Pale coloured crystal opals (white crystal opals) are generally more valuable than opaque white opals, and ‘black crystal opals’ can often have more beautiful colour than opaque black opals.

    • Crystal opals are generally cut in a standard oval shape if possible, however if the nature of the stone dictates, sometimes a ‘freeform’ or teardrop shape is cut in order to maximise the size and carat weight of the stone. Crystal opals are also cut with a high cabochon if possible as this enhances the appearance of the colour. When cutting light opal we yield 50% which means we only have a 50% loss factor due to rock waste.
  •  

White or "lIGHT" Opal

The most common form of opal is Coober Pedy’s White Opal.
Representing approximately 60% of all opal mined, white opal is exported and recognized all over the world.

White_opal
    • White opal contains Magnesium Oxide which is what gives the opal its white base. Because of their pale body tone, white opals generally have less vibrant colour than boulder opals and black opals. They do not have the advantage of having a dark or black background which enhances the stone and makes the opal colour stand out.
    • When a white opal is partially translucent, it enhances the clarity and vibrancy of the colour, and thus the value of the stone. Therefore a white opal which has some of the properties of a crystal opal will often have a higher value.
    •  
  • The home to the light opals, Coober Pedy was discovered in 1915. It is an isolated and rugged location with freezing nights, days where the temperature rarely drops below 40 degrees Celsius with bush flies by the million. Because it is too hot for life to exist comfortably on its surface, many homes have been built underground. Virtual palaces, a church and even a hotel have been built underground where the living temperature stays at a cool 20-24 degrees Celsius. A miner gouging out an underground dwelling can often find the exercise self-funding when he hits an opal seam. Today the opal fields in Coober Pedy are approximately 45 kilometers.

“Common” or non-precious Opal

Precious opal shows a play of spectral colours though the stone whereas common opal does not. Common opal is usually opaque to translucent and brownish orange in colour, however it can come in any colour, some of which are quite attractive. Agate Opal is the banded variety of common opal which can form in opalised fossils or in veins. Dendritic or Moss Opal is where moss like (dendritic) inclusions are formed of different iron minerals encased by the opal producing these aesthetic designs. Other names include ‘landscape’ opal in which the branch like structures of the iron minerals resemble that of a woodland landscape.

 

pink opal gemstone parcel

Pink Opal

Pink opal is a common opal in pale to bubblegum pink, though other colors like white, yellow, peach, lavender, and black may appear as well. This opal type commonly has inclusions that create dark streaking or color zones.

Pink opals come from Australia, Mexico, and the USA, but Peru is the most prolific source. Peruvian pink opals have a milky tone and vivid, uniform color, particularly “pink Andean opal.”

Western Australia’s pink opals are actually opalized radiolarite and often heavily included (meaning they have trace quantities of other minerals or debris), creating white, brown, or black patterns. 

purple morado opal bead strand

Morado Opal

Morado opal, also called “purple opal” or “Opal Royale,” is a purple common opal variety native to Mexico. The colors range from lavender to violet, and are typically milky and opaque in tone. Purple hues also appear in Tiffany opal, an opal fluorite conglomerate from Utah, USA, colored purple by fluorine gasses. 

peruvian deep blue opal

Blue Opals

Blue opals can be common or precious, ranging from deep teal to pale sky-blue. Peru is largely tied to this variety, and “blue opal” often refers to Peruvian common blue opal. Peru also produces precious blue opal, and some stones have play-of-color in small zones. 

Brazil joins Peru in producing a rare blue-green opal called Paraiba opal. Other blue opal mines are in Slovakia, Indonesia, and the USA, including Oregon’s pastel blue Owyhee opals. 

tanzanian green opal rough

Green Opals

One common opal found worldwide is green opal, seen in striking shades of emerald, yellow-green, or muted jade. Found in six continents, the most prominent mines are in Australia, Brazil, Peru, Mexico, and the USA.

Common Green Opal Cabochon Gem A Blog The Different Types of Opal Photograph by Henry Mesajpg

Common green opal with dendritic inclusions, also known as moss opal. Photograph by Henry Mesa. 

Some of the more sought after common opal comes from Peru. Very pretty blues, pinks and bluish greens can be found there. These come from the two main provinces: Ica and Caraveli. The best blues come from Caraveli and are known as Andean opal. Ica produces the better pinks, but both mines produce both colours.

Natural opalite is another green common opal variety, though it also shows shades of purple. Opalite is typically mossy-green with dark dendritic inclusions and can show chatoyancy (the cat’s eye effect.) Most specimens come from Africa, but Ethiopia’s cat’s eye opalite is often honey or yellow.

One more type of green opal is Tanzanian prase opal. This variety contains nickel, which gives the stone a glowing neon teal color. Prase opals are translucent to transparent, and some call them “African jade.”

Next up, what color opal is most valuable? That would be red opal, which also happens to be the most valuable color of fire opal.

precious fire opal

Fire Opal

Do you love a fiery spectacle? You’ll find precisely that in fire opals. Fire opals come in red, orange, yellow, and brown body colors and can be either common or precious. Originating in Mexico, these stones are often called Mexican fire opals, though they also come from Australia and Ethiopia.

Fire opals differ from most opals in being translucent to transparent (not opaque) and forming inside volcanoes. Most Mexican fire opals are common opals, but Ethiopia produces precious fire opals with neon violet and green color flashes.

faceted crystal opal

Colorless Opal

Outside the rainbow, we have colorless opal types. While they may lack color seen in the opals mentioned above, they each offer unique properties.

  • Crystal Opal: Any precious opal that is colorless and transparent, with no milkiness and N7-N8 on the body tone scale.

  • Jelly Opal/Water Opal: Transparent, colorless precious opals that are slightly darker than crystal opals and have a gelatinous appearance, sometimes with an internal play-of-color and blue or golden sheen.

  • Water Opal is the colourless variety of precious opal and can have a soft appearance. Usually the play-of-colour appears to be inside the stone against a colourless transparent background, which means it can appear minimal. The best examples are from Mexico, other localities include Australia and the USA

  • Contraluz Opal: Translated from Spanish as “against light,” colorless precious opals show play-of-color floating inside the opal when you illuminate the stone from the back.

Moving into the next category, we have opal types defined by forming with other materials. 

African Opals

In recent decades the discovery of several opal deposits in Ethiopia has landed Africa as an important source on the opal map.

mexican fire opal rough parcel

Central & South American Opal

  • Mexican Opal: Mostly known for fire opals, but Mexico also produces madera opals, contra luz opals, cantera boulder opals, and some of the world’s best water opals.

  • Brazilian Opal: Known for crystal opal with pastel color flashes and low moisture content. 

  • Peruvian Opal: Known for blue or pink Peruvian opal, which is also the country’s national stone.

  • Honduran Opal: Recognized for holding the world’s oldest opal mines and producing unique boulder and matrix opals.

virgin valley american opal

Other Locations

  • Indonesian Opals: Known for natural opalite and opalized wood.

  • American Opals: Mostly from Idaho, Utah, and Virgin Valley, notable American varieties include Owyhee opals, “Thunderegg” opals, rainbow opals, dendritic opals, opalized wood, hyalite, banded opals, Louisiana sand opals, and Utah bacon opals. 

  • Slovakian (or Hungarian) Opals: Distinct white precious opals with internal blue and orange color flashes.

Other Opal Types

Some opals don’t fall neatly into a category, but they shouldn’t be overlooked! 

opalized fossil parcel

Opalized Fossils

Like Jello molds, silica solution fills fossil imprints left in rocks and hardens into an opalized fossil! These opals can form in fossils of animal skulls, shells, pineapples, and even 100-million-year-old squid called opalized belemnite. While mostly found in Australia, miners have found opalized fossils in the USA, Hungary, and Indonesia.

What’s the most expensive opal? Believe it or not, an opalized fossil! The Virgin Rainbow is known as one of, if not the most expensive opal in the world at over $1 million. It’s actually an opalized fossil of an extinct cephalopod named belemnitida. 

hyalite opal specimen

Hyalite

Hyalite is a unique type of opal called opal-AN, an amorphous opal with a network-like structure similar to glass. This colorless, pale yellow or green common opal variety doesn’t have silica spheres and won’t display play-of-color unless it has inclusions.

Hyalite’s most distinguishing feature is green fluorescence caused by its uranium content. The strong glow appears in UV light or direct sunlight.

COMPOSITE OPALS – DOUBLETS & TRIPLETS

DOUBLETS

A great way to start enjoying opal at a fraction of the cost of a solid opal is to go for a composite or enhanced opal such as the doublet or triplet opal. A doublet opal, as the name suggests consists of two layers. The first layer is a thin slice of natural crystal opal and the second layer can either be potch or ironstone – the natural backings that black and boulder opals originally form in. The crystal opal is stuck together with black cement and attached to the potch or ironstone in effect enhancing the colours and patterns of the crystal opal.


Doublets can usually be identified by looking at the side of the opal – if the layers are adhered together you will notice that the line where the coloured opal and the black backing meet is perfectly straight. This is necessary for the two layers to be adhered together. If a doublet is set into jewellery with the sides covered, it is extremely difficult, even for an expert, to tell whether it is a doublet or a solid opal. Since the top of the stone consists of pure opal, it therefore appears exactly like a black opal, and doublets thus have a much more natural appearance than triplets.

doublets

TRIPLETS

A triplet opal consists of three layers. It is in fact a doublet with a crystal quartz cap which adds the third layer and becomes known as a triplet. The crystal quartz cap sits on top of the thinly sliced crystal opal. It acts as a lens that magnifies and enhances the patterns and colours of the crystal opal.

 

 

Because triplet opals have a clear non-opal capping on top, it is easy for an experienced person to identify a triplet immediately by the appearance of the triplet opal.

 

 

Triplets usually have a ‘glassy’ appearance and the light reflects differently from the top of the opal. You can look at the side of the stone to identify a straight line where all the layers meet, and also look at the back of the opal.

 

 

Triplets are generally the less expensive option out of the two because there is less weight of opal, however of all the forms that opal is available, triplet opals, because of the higher refractive index of the quartz crystal cap and the magnifier effect of its domed shape – opal triplets show the most ‘bling’

 

 

triplets

CREATED OPAL AND IMITATION OPAL

SYNTHETIC OR LAB CREATED

A triplet opal consists of three layers. It is in fact a doublet with a crystal quartz cap which adds the third layer 

and becomes known as a triplet. The crystal quartz cap sits on top of the thinly sliced crystal opal. It acts as a 

lens that magnifies and enhances the patterns and colours of the crystal opal. Because triplet opals have a clear 

non-opal capping on top, it is easy for an experienced person to identify a triplet immediately by the appearance 

of the triplet opal.

This type of gemstone is created in controlle laboratory conditions.They have the same chemical composition and physical properties to that of the natural gemstones. Various methods are used to create synthetic gemstones. The laboratory opal producing process, was first invented by Pierre Gilson, Sr. of France in 1974. This process produces a kaleidoscope of colors. From the rare and precious black opal, to crystal and white opaque opal. The Gilson formula is considered the truest gemological process in the world today. Considered by many gemologists to by the world’s finest laboratory grown Opal. This process takes from 14 to 18 months, and the colors are natural with no treatment or enhancements. Triplets are generally the less expensive option out of the two because there is less weight of opal, however of all the forms that opal is available, triplet opals, because of the higher refractive index of the quartz crystal cap and the magnifier effect of its domed shape – opal triplets show the most ‘bling’.

 

The words “synthetic,” “simulant,” and “imitation,” can confuse buyers. They all refer to man-made opals, but simulant opals have the same chemical composition as natural opals, while imitation opals only share a similar appearance. 

In gemological terms, “synthetic” strictly refers to simulant opals. One exception is synthetic opalite, a man-made, opalescent glass resin. 

The most common synthetic opals manufactured are black or white opals, but various simulant and imitation varieties have emerged:

Monarch Opal – A New Man Made Synthetic Opal

Monarch Opal - A New Man Made Synthetic OpalThis new man made synthetic opal is popular in low end silver settings as the designs and patterns look amazing with veined potch lines. Many online sites and retailers sell it as Monarch Opal and do not inform buyers if it is man made, synthetic or natural. When buyers ask about this opal in a setting they are told it is simply Monarch Opal. It has also been given the names of Galaxy Opal, Monet Opal and Exodus Opal.

To be accurate, this Opal is actually called Sterling Opal. The names above such as Monarch Opal are trade names given to the different varieties of Opal that they can create.

Many synthetic opals have unnatural appearances and the developer of this opal has gone to considerable lengths to make veins and patterns as close to natural a s possible. The Monarch Opal is created by the same man that developed the Zachery Process for Turquoise. His name is Jim Zachery.

The potch lines are black and are random like a natural opal, and some patterns are like snake or honeycomb pattern that is in Ethiopian opal. The moulds are 40 mm in size for the mixture to grow in. Nano silica in micro spheres in silica are grown and no dyes are used to make these opals. This makes the opals similar but different just like natural opal with veins and patterns and different light reflection patterns.Monarch Opal - A New Man Made Synthetic Opal

Rough Monarch opal is available and thick 10mm slabs, which is hard to find in nature. Some monarch opal is plain and no distinct pattern, so can be bit confusing. Monarch opals are not allowed to be sold on Opal Auctions and our Opal Sheriff program, which is operated by gemmologists, monitors so that none are listed. Monarch opal has been tested by GIA to be a synthetic opal

  • Aurora Opal: Partly synthetic opal composed of silica and resin, available in seven body colors and displaying one-of-a-kind swirling patterns.

  • Dragon’s Breath Opal: Imitation opal with opalescence but no play-of-color, composed of Czechoslovakian glass and appears ruby-red but shifts into blue and purple hues when turned.

black opal mixed parcel

 
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