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Mineralogically, opal is a hydrous silicon dioxide with a chemical composition of SiO2.nH2O. It is amorphous, without a crystalline structure, and without a definite chemical composition (it contains a variable amount of water, as shown by the “n” in its chemical composition). Therefore opal is a “mineraloid” rather than a “mineral.”

Opal Characteristics

  • Hardness: 5.5 – 6
  • Color: Colorless, white, yellow, red, orange, green, brown, black, blue, pink
  • Transparency: opaque, translucent, transparent
  • Chemical composition: SiO2·nH2O
  • Crystal system: Amorphous
  • Crystal habit: Irregular veins, in masses, in nodules
  • Refractive index: 1.45

History of Opal

Many cultures have credited opal with supernatural origins and powers. Arabic legends say it falls from the heavens in flashes of lightning. The ancient Greeks believed opals gave their owners the gift of prophecy and guarded them from disease. Europeans have long considered the gem a symbol of hope, purity, and truth.

The name of this, the traditional October birthstone, is believed to have originated in India (the source of the first opals brought to the Western world), wherein Sanskrit it was called upala, a “precious stone.” .” In ancient Rome, this became opalus. Most opals are valued for their shifting colors in rainbow hues – a phenomenon known as “play-of-color.”

The October birthstone’s dramatic play-of-color has inspired writers to compare it to fireworks, galaxies and volcanoes. Bedouins  once believed opal held lightning and fell from the sky during thunderstorms. Ancient Greeks thought opals bestowed the gift of prophesy and protection from disease. Europeans long maintained opal to be a symbol of purity, hope and truth. Hundreds of years ago, opal was believed to embody the virtues and powers of all colored stones.

Opal is also the stone given to celebrate the 14th wedding anniversary.

Opal Formation

Opal is formed from a solution of silicon dioxide and water. As water runs down through the earth, it picks up silica from sandstone, and carries this silica-rich solution into cracks and voids , caused by natural faults or decomposing fossils. As the water evaporates, it leaves behind a silica deposit. This cycle repeats over very long periods of time, and eventually opal is formed.

Sources of Opal

The opal birthstone can be found in many places. The fields of Australia are the most productive in the world for the October birthstone. Ethiopia, Mexico and Brazil are also important sources. Additional deposits have been found in Central Europe, Honduras, Indonesia, Madagascar, Peru, Turkey and the United States.

Lightning Ridge, a small town in New South Wales, Australia, is famed for producing prized black opal. A dry and rocky region softened only by small trees and scrub brush, Lightning Ridge gets little rain and bakes in the scorching summer temperatures. The climate is so unforgiving that miners often live underground to find respite from the punishing heat.

Opal Varieties

Opal is a very common material, found throughout the world. Most opal is “common opal” or opal that lacks the colorful flashes known as “play-of-color”. Some people use the name “potch” for this type of opal.

Most common opal has an unremarkable appearance and is almost invariably overlooked in the field. It is often assumed to be quartz or a variety of chalcedony – but a surprising amount of common opal exists.

The rare specimens of opal that exhibit a play-of-color are known as “precious opal”. If the play-of-color is of high quality and large enough to cut, the material can be used to produce valuable gemstones.

If you examine a specimen of precious opal under bright light, play-of-color can be observed in three situations: 1) when the stone is moved, 2) when the light source is moved, or, 3) when the angle of observation is changed. The video near the top of this page illustrates the beautiful “play-of-color” in an Ethiopian Welo opal.

The word “opalescence” is often misused. Some people believe that “opalescence” and “play-of-color” are the same, which is not true. The common definition given for opalescence is “the pearly luster of common opal”. In truth, the most common opal does not have a pearly luster, even when it is polished.

Red, orange and yellow are the most desired spectral colour to be seen in opal and therefore command higher prices. Blue and green are less desirable colours, although still beautiful. 


This is the most ubiquitous variety of opal. It has a white background and is sub-transparent to translucent and usually displays opalescence. The best examples will show all the spectral colours. It is now considered to be less valuable than black opal.

However fine white opal still commands high prices and is very attractive. Most white opal comes from Marla, Australia and Whitecliffs, Australia, but is also found in Hungary, Ethiopia and Canada.


Displaying a black body colour with little to no opalescence, this variety is now the most desirable. The black background allows the yellows, oranges and reds to ‘pop’ in contrast to the dark background, supposedly making the play of colour more impressive.

Once again the intensity and fullness of the play-of-colour contributes to the pricing. Black opal predominantly comes from Lightning Ridge, Australia, but can also be found Hungary, Honduras and the USA.


These varieties occur when opal forms in narrower veins and is cut and polished within the host rock. Boulder opal was first discovered in Queensland, Australia, it can also be found in Brazil and Canada.

Benefits of Opal

Opal crystal is mostly known for its ability to bring person characteristics and positive traits to the surface. It is believed that Opal stone can pick up persons thoughts, desires, feelings and emotions and amplify them. Negative feelings and emotions that are picked up by Opal crystal, even though they are unpleasant and uncomfortable, are easier to understand, process, and fix. This stone will assist and help you get rid of negativity and those feelings that bother you.

Opal helps in leading a luxurious life. It brings prosperity and supports gaining a good reputation in the society. It is said to flourish businesses in the field of travel and tourism and import-export. It is also believed to aid in clearing debts and litigations.

Opal helps in clearing issues in a marriage and provides marital bliss. It is thought to help in finding a suitable match.

Opal is also believed to help overcome emotional setbacks or sufferings caused by past relationships. It helps in calming the mind and make peace with the past.

It eases nightmares and helps the wearer sleep peacefully.

It aids in curing intestine and stomach problems, like indigestion and acidity. Opal is also said to cure pancreatic and hormonal problems.

Opal is thought to cure eye-related problems and keep eyes healthy and grant an excellent immune system.

It is considered to enhance the creativity and artistic abilities of a person.

Opal is believed to bring good fortune, peace, joy, and wealth to the wearer.

Opal helps the wearer to have a pleasing personality. It assists in gaining self-confidence and utilise one’s potential to fullest.

Care Instructions

Solid opal should be cleaned gently with mild detergent in warm water and a soft toothbrush or cloth. Avoid bleach, chemicals and cleaners. Doublets & triplets may be wiped with a damp soft cloth and mild detergent, but should never be soaked or immersed.

Never allow anyone to clean your opal in an ultrasonic cleaner, as the intense vibrations may cause cracking in a solid opal, and water penetration in a doublet or triplet.

If your stone loses its shine or becomes scratched, bring it back to an opal cutter. After years of wear, small scratches and scuff marks cause an opal to lose its shiny polish and become dull looking. Professional polishing can bring new life to an opal which has become dull or scratched, and we can also check for claw damage and ensure the security of the setting.

If you need to store your opal away for a period of time, simply place it in a padded cloth bag for protection and store it away. For longer storage periods, place your opal in cotton wool with a few drops of water, then into a sealed plastic bag just to be safe. The water is not intended to soak into the stone (as opal is impervious) but will prevent water coming out of the stone if it is exposed to very low humidity environments (for example, zero humidity storage safes).