Common Opal

Common opal, also called "potch" by opal miners, is opal that does not show play-of-colour. Like precious opal, it is hydrated, non-crystalline silica, but its tiny silica spheres are arranged irregularly, so light is not split into rainbow flashes. Common opal is far more abundant than precious opal and is found in many colours, often with a soft, milky or waxy appearance.

Many common opals have attractive colours and are popular for beads and cabochons. Pink opal and blue (Andean) opal from Peru are among the best known, with soft pastel colours. Other varieties include green opal (often coloured by nickel), yellow and honey opal, white milk opal, wood opal (where opal has replaced fossil wood), dendritic opal (with fern-like black inclusions), hyalite (clear and glassy, often fluorescent) and black common opal.

Peruvian opal is found in the Andes and has been used by local cultures for centuries. Other important sources include Mexico, Tanzania, Madagascar, Australia, Brazil, Slovakia and the USA. Some "pink opal" on the market is actually palygorskite or another mineral, and some common opal is dyed.

Common opal is generally more stable and less likely to craze than precious opal, but it is still relatively soft and should be handled with care.

Common Opal at a glance

Caring for common opal

Common opal is relatively soft (5.5 – 6 on the Mohs scale) and contains water. Clean it with lukewarm soapy water and a soft cloth. Avoid ultrasonic and steam cleaners, high heat, sudden temperature changes and household chemicals. Store it separately from harder stones in a soft pouch.

In folklore

The beliefs below are traditional folklore, included for interest. They are not scientifically proven, and nothing here is medical advice.

Peruvian blue and pink opal has been used in Andean cultures for centuries and is the national stone of Peru. In folklore, opal of all kinds was linked with hope and purity, and the clear, glassy hyalite opal was once called "Muller's glass". Common opal is associated with the zodiac sign Libra and with Cancer.

Common opal is traditionally regarded as a gentle, soothing stone. Crystal healing lore holds that it brings calm, emotional balance and a sense of peace, and encourages communication. Each colour is given its own meaning: pink opal is associated with love and healing the heart, blue opal with calm and communication, and green opal with renewal and growth.

Related stones

Precious opal, fire opal, Peruvian blue opal, pink opal, green opal, wood opal, dendritic opal, hyalite and moss opal. Stones that can look similar include chalcedony, chrysoprase, rose quartz, larimar, amazonite and dyed glass or resin.

For the technically minded

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