Types of Opal

When choosing an Opal, especially  for the first time, its very important to understand that not all Opals on offer are the same.  Some have  taken millions of years to form and can last many generations. While other types of Opals are manmade and can lose their beautiful colours within a very short time.

Below is a brief guide on some of the more common types of Opals

 

Natural Solid Opal

Natural Solid Opal is any Opal that has not been changed  from its natural state -- except to be cut and polished into a gem stone. The best know types are Queensland Boulder Opal, Black Opal, Crystal Opal, White Opal. Opal can also be found in Mexico and Ethiopia. Natural Solid Opals are the most sort after types of Opals.

Australian Boulder Opal

Boulder Opal is uniquely found in small pockets of ground  in western Queensland, Australia. The name Boulder Opal comes from the combination of Ironstone/sandstone rock and a seam of precious Opal which was formed in crevices inside the ironstone/sandstone rock, often giving the opal an uneven surface that further enhances the array of colours.

The material is cut and polished with the opal material still attached to the parent material (e.g. ironstone) on which the opal formed. Boulder opal presents beautifully in jewellery of all types, including men's jewellery.

 

An  example of Boulder Opal rough, imagine the thrill of sorting through opal rough, not knowing what beautiful opal you will find.

Side view of a Boulder Opal polished stones - notice the uneven way the opal and Iron stone has formed.

 

 

 

 

 

 

 

 

 

 Because of the toughness of the Boulder Opal, a simple round hole can be drilled into the side of the rock  to make a natural looking and  long-lasting Opal pendant.

 

 


 

 

 

 

 

 

 

Above are examples of the many colours found in Boulder Opal.These amazing Opals were found near the town of Winton in Outback Queensland

When the Iron stone is visible alongside specs of Opal, it is called Boulder Opal Matrix. Boulder Opal Matrix especially from the mining areas of Koroit and Winton can have beautiful amazing patterns. 

 

 

 

 

 

 

 

 

Example of Boulder Opal Matrix from western Queensland

 

Australian Black Opal

Australian Black Opal is one of the most well-known and most valuable types of any Gem Stone.

A Black Opal has a black or very dark grey body tone or background to its appearance.

The darker the body tone of  the Black Opal will mean the Opal colours speckles will stand out more enriching the beauty of the stone.

The most famous Black Opal mining area in the World is Lightning Ridge NSW, Australia.

Natural Australian Black Opal set in Diamond and Gold ring

 

Australian White, Light, and Crystal Opal

White opals have a white base, and the colour play and patterns present themselves in this white opal base. Opals in this category can host a wide variety of colours and light play patterns. White opals are the most common type of opal and can be found in all the Australian Opal fields.  The Australian Opal Shop always has a good selection of white Opals and customers are amazed by the many colours. 

Crystal Opal, the colour play presents itself against a transparent or translucent opal base. A rough rule is a printed page will be visible through the stone. Light can pass through a crystal opal and light opal.

 Australian White Opal set in Diamond and Gold  pendant and ring

 

Koroit  Opal Matrix

Koroit Opals are found exclusively in the opal fields of Koroit,  Australia. These durable stones are among the hardest opal material of all Opal types. Unique, artistic design and beautiful patterns of vibrant colour are characteristic of Koroit boulder opals. They make stunning pendants and rings, and they stand out in a any gem collection.

Koroit Opal Matrix set in Gold and Diamond Pendant

 

Australian Sandstone Opal Matrix  

GIA article for Australian Opal Matrix link

In some Opal mining areas of Australia, Opal can form in the Sandstone layers below the ground. This is called sandstone Opal Matrix. This type of Opal Matrix , often found in western Queensland (another type is also found in Andamooka South Australia), can be cooked in cooking oil resulting in the sandstone  becoming darker or black colour Cooking the sandstone matrix in this way will make the Opal colours look more vibrant and make any patterns formed by the Opal speckles more visible. 

 

Natural Sandstone Opal Matrix Beads 

 

Cooked Sandstone Opal Matrix Beads, look at
the beautiful blue and green Opal speckles.

 

Hydrophane Opal (sometimes called Water Opal)

The name is given to Opals that absorb water (many household liquids such as cleaning products and lotions should be avoided when wearing Hydrophane Opal).

If Hydrophane Opal is soaked in water,  the water is absorbed  into the Opal. As a result any play of colour(fire) will seem to have disappeared.  Colour will return once the Opals dries out.

Direct contact  to the skin should be avoid when wearing  Hydrophane Opal, as the bodies natural moisture will be absorbed into the Opal, and colour lost.

The  stone on the top picture is a Natural Ethiopian Hydrophane polished Opal which is dry, and the bottom photo is the same stone again after been submerged in tap water for 10 minutes. Notice the  Hydrophane Opal has become transparent after contact with water, and the Opal colours appears less

 

Treated  Black  Hydrophane Opal

Although natural Ethiopian Black Opal has been found,  when purchasing Black Ethiopian Opal today you must purchase on the belief  that nearly all Black Ethiopian Opal have been treated. The appearance can look similar too natural Australian Black Opal but treated Ethiopian  Black Hydrophane Opal will only be a fraction of the price. 

 

Natural Ethiopian Hydrophane Opal  polished beads

treated Ethiopian Opal

Treated  Ethiopian Hydrophane Opal  polished beads

The Australian Opal Shop does not sell Hydrophane Opal 

 

Doublet Opals

A doublet opal is comprised of two layers, a top layer of real, natural opal glued to a bottom layer of darker stone. Ironstone or black onyx is often used for this second layer.

A rough rule when purchasing  Opal Doublet jewellery is that the value should be around  10% value of a Solid Natural Opal of similar quality and size.

The Australian Opal Shop does not sell Opal Doublets

 Opal Doublet that has been chipped

Opal Doublet that has been chipped

 

Opal Doublet side view, notice that the join between the Opal slice and the brown sandstone rock is very flat and smooth,  this is to make it easier to glue. Where as a solid natural Boulder Opal the join between Opal and host rock will be uneven.

 

thickness of opal in opal doublet

A slice of Opal ready to be glued and made into an Opal Doublet

 

 

Triplet Opals

A paper-thin slice of Opal, glued on a stone backing, and a clear crystal dome top.  After making, Triplet Opals will display  bright colours, but can be ruined easily by getting wet regularly, eventually the glue that holds the Triplet Opal together will become cloudy and any Opal colours will disappear.

The Australian Opal Shop does not sell Opal Triplets

 

side view opal tripletOpal triplet side view - 3 layers - can you see them.

(1.Top - glass dome, 2.middle - opal slice,3. bottom-- thin black backing)

 

opal triplet thickness
The thickness of the Opal in a Opal triplet can be as little as 0.18mm
Opal triplet with nice colour

A Opal triplet that has become cloudy and lost its colour

 

 

Synthetic and laboratory Opal (Fake Opal)

Man made resin, made to look like natural Opal. 

Examples of Synthetic and laboratory Opal