About Opal

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Keep reading to discover more about opal

  • Mineralogy and geology*
  • Metaphysical, Spiritual and Healing** Properties***
  • Common Associations


Mineralogy* and Geology of Opal

Chemistry: SiO2 · nH2O

Color: clear, white, yellow, red, orange, green, brown, black, blue

Luster: vitreous, waxy, greasy, dull

Diaphaneity: translucent to transparent

Moh’s scale hardness: 5 ½ - 6 ½

Specific gravity: 1.9 – 2.3

Streak: white

Cleavage: none

Fracture: irregular, uneven, splintery, conchoidal

Named after: The origin of the name is uncertain. It may be from the Sanskrit "upala", meaning "stone" or "precious stone" or from opalus, the ancient Latin name for the gem (Pliny the elder, 75-79). Pliny may have also referred to the gem as paederos, but a modern commentary by Kostov (2008)[1] questions if that name was actually applied to the opal of modern sense.

Geological occurrence: Opal occurs in altered volcanic tuffs and basalts. It also occurs in silicious deep-water marine sediments. Opal-C, opal-CT and opal-AG formation is restricted to low pressure and low-temperature environments. 

Opal is a hardened silica gel, and usually contains 5-7% water in submicroscopic pores. Its structure varies from essentially amorphous to partially crystalline. Precious opal is the least crystalline form of the mineral, consisting of a regular arrangement of tiny, transparent, silica spheres with water in the intervening pores. 


Technically opal is not a mineral – it has no regular crystalline structure. It is a mineraloid, like volcanic glass, moldavite, obsidian, coal and jet. The formula for opal is SiO2 · nH2O. This reflects its structure – spheres of silica with interstitial molecules of water. It is softer than quartz (SiO2) with a hardness (Mohs scale) of 5½ - 6½. Opal is inherently unstable, subject to cracking (denaturing of the water in the stone) and scratching, so may require special care as either jewelry or collectible specimens

Precious opal forms only in undisturbed pockets within another rock that hold an aqueous solution of relatively pure silica from which water is slowly removed over a long period of time. If undisturbed, the spheres of silica gel and interstitial water molecules can become more ordered, creating the play of colors seen in precious opal (particular colors due to the spacing of spheres).

Forms and Types of Opal

Common or “potch” opal has no special coloring, and no play of color, and is often more opaque than translucent. Varieties include resin opal (honey-colored), wood opal (wood petrified with opal), hyalite opal (glass-clear opal, such as that found in Spirit Cave geodes), geyserite (also called siliceous sinter) found around hot springs or geysers, and diatomaceous earth (consisting of the shells of innumerable diatoms, a form of marine plankton).

“Precious” opal is translucent, and shows an iridescent play of colors when viewed from different angles

“Fire” opal has a reddish color, and is typically found in Mexico. Some fire opal is also precious.

“Black” opal has a gray to dark blue-black matrix that contains the opalescent fire.

“Opalite” has become popular in many rock and metaphysical shops, usually found with carvings and tumbled stones. It is a synthetic glass that simulates the appearance of opal, and is both less expensive and easier to carve and shape.

“Opalina”, “Peruvian opal” and “pink opal” are naturally colored varieties of opal that come from the Peruvian Andes. Peruvian opal comes in shades of pink, green and robin’s egg blue; in the less gemmy form of this (opalina) the blue is interspersed with lighter colored matrix material. Gemmy varieties occur as well.

“Doublet” or “triplet” opals consists of two or three thin layers of opal glued together to make a cabochon. This takes natural precious opal that is in layers too thin to work and creates a beautiful gemstone.  Many Spencer opal cabochons are formed this way.

Opal Geology, History and Uses

Precious opal deposits occur in either volcanic rocks or in sedimentary rocks. In both, silica-rich waters, typically of surface origin, have penetrated into the subsurface, precipitating when they find an open space or cavity, sometimes in fractures. The waters may be unusually rich in silica because the overlying rocks have been so intensely weathered. Once the silica-rich waters start accumulating in the cavities, they start evaporating, leaving behind a colloidal silica gel, that eventually hardens into opal.

The Australian deposits of the Coober Pedy, Andamooka, and Mintabie areas are examples of sediment-hosted opal.  The opal deposits of Mexico, Honduras, Spencer (Idaho), and Ethiopia occur in silica-rich volcanic terrane.

Other types of opal are abundant near active hot springs. Because the siliceous skeletons of diatoms, radiolarians, and sponges are abundant in some sedimentary rocks, opal constitutes important parts of many sedimentary accumulations such as diatomaceous earth. It is commonly found as fossilized wood where it preserves the wood's external appearance and cellular structure. 

Until late in the 19th century, the primary source of precious opal, including that used by the Romans, was in present-day Slovakia, where opal occurred in andesite. Today, the major producers of precious opal are Australia and Ethiopia.

Today, the chief producer of precious opal is Australia, where it was discovered in 1887, with deposits in South Australia, Queensland, and New South Wales.

Opal from Australia – Australia has been a source for much of the world’s opal, including precious white and black opal. Black opal from the Lightning Ridge site in New South Wales is world famous. Boulder opal, from western Queensland, consists of a brown ironstone matrix with fractures filled with precious opal. Andamooka opal, from South Australia, is also famous. Read more about boulder opal HERE.

Opal from Ethiopia -  Although opal from the area of present-day Ethiopia has been known and used by humans for thousands of years, the first modern-day report of gem opal appeared in 1994. This opal was highly subject to cracking and was thus unpopular in the gem trade. In 2008 a new deposit of gem opal was found in the Wollo province that was better suited for jewelry. This type of opal is now referred to as “Welo” opal. Read more about Ethiopian opal HERE and HERE.

Opal from North America – The western third of North America contains abundant silicic volcanic rocks, so it’s no surprise that opal (both potch and precious) is found from Oregon, Idaho, and Nevada, to Mexico. In Idaho,

Spencer (Mine) Opal, from Idaho, is typically seen as doublets and triplets. The opal occurs in a rhyolite obsidian flow. Read more about Spencer opal HERE.


Spiritual, Metaphysical and Healing Properties

Opal is considered an October birthstone. Some people think it’s unlucky for anyone born in another month to wear an opal. But that particular superstition comes from a novel written in the 1800s (Anne of Geierstein by Sir Walter Scott), and not from any ancient belief or experience. In fact, throughout most of history, opal has been regarded as the luckiest and most magical of all gems because it can show all colors.

What would it look like if rainbows were shimmering in water? This watery quality of opal’s appearance relates to its ability to affect the emotional energy field. Opal traditionally also relates to visions and sight. Like its compositionally related sister, quartz, opal amplifies energy.

In Melody’s Love Is in the Earth Encyclopedia (the big book), the energetic properties of about 27 different kinds of opal are discussed over 15 pages (pp 528-544), so if you can find a copy of this out-of-print treasure, have a look! She calls opal a “stone of happy dreams and happy changes” referring to opal’s traditional uses with having visions (as in meditation) and in gently amplifying one’s traits so they can be noticed and changed.

To intentionally work with opal, note its color and find the chakra associated with that color.

  • Peruvian opals in shades of pale green to blue work with heart and throat chakras, soothing and energizing these areas.
  • Pink and orange opal, associated with sacral to heart chakras, helps to increase energy levels and to lift moods.
  • Precious opal with rainbow colors, associated with third eye to crown chakras, helps with intuition and meditation, improving stability and flow of energy through those centers.
  • Common (potch) opal can be different colors; all help stabilize the emotions and provide a lift in self-love.

Feng Shui of Opal

Feng shui is the ancient art of enhancing the energy of your home or work space by intentional placement of objects and features. 

The inherent energy of minerals and crystals, as well as their color and/or shape, makes them perfect as additions to the feng shui of any space. Opal’s connection with vision make it an excellent addition to any place where you meditate, and to altars.

Opal can help with insights about career and life path if placed in the corresponding part of your home or office. The bagua is a map of the energy centers of your space, divided into 8 areas around the center. Standing at the entrance to your space, the middle third of the area closest to the entrance relates to career and life path. Placing opal in this area may help with making choices about career and life path.

Wearing Opal

Opal gently energizes and supports whatever area of the body it’s close to, so set that intention when you put on your earrings, pendant, bracelet, necklace or ring. Keep in mind that opal is prone to fracture when selecting your jewelry.

Opal Lore

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 against disease. Europeans have long considered the gem a symbol of hope, purity, and truth. Once, it was thought to have the power to preserve the life and color of blond hair. Opal was associated with sight; carrying an opal wrapped in a fresh bay leaf would keep others from seeing you. This superstition earned opal the popular designation of patronus furum, Latin for “patron of thieves.”


 Common Associations for Opal

  • Color:  various

    Chakras:  depends on color

    Numerology: vibrates to 8

    Planets:  Venus

    Zodiac:  Cancer, Libra, Scorpio, Pisces, Snake

    Bagua:  Career (Kan)

    Elements:  Water

    Birthstone:  October

    Wedding Anniversary: 34th


* Mineralogical information is from mindat.org

** Always consult with your medical professional for any physical or long-term healing issues.

*** Metaphysical properties come from: 

Love Is in the Earth (1995) Melody, Earth-Love Publishing House, 726 pp.

The Crystal Bible, A Definitive Guide to Crystals (2003) Judy Hall, Walking Stick Press, 399 pp.

Crystal Muse (2017) Heather Askinosie and Timmi Jandro, Hay House, 285 pp.

Crystal Gridwork (2018) Kiera Fogg, Weiser Books, 128 pp.