Opal, with its captivating “play-of-color,” is a unique and beautiful gemstone, admired for its iridescent dance of hues. While its visual appeal is undeniable, many express concern regarding its durability. Understanding opal’s strength and best practices for its care can help preserve its beauty for generations. This article clarifies opal’s characteristics and provides practical guidance for its longevity.
Understanding Opal’s Durability
Understanding gemstone strength involves differentiating between two properties: hardness and tenacity or toughness. Hardness refers to a material’s resistance to scratching, measured by the Mohs scale of hardness. Tenacity, also known as toughness, describes a gemstone’s resistance to breaking, chipping, or fracturing when subjected to impact.
Opal typically ranks between 5.5 and 6.5 on the Mohs scale, placing it in a similar range to glass. For comparison, quartz, a common mineral, rates at 7, while diamond, the hardest known natural substance, scores a 10. This Mohs hardness means opal can be scratched by harder materials, including common dust particles which often contain quartz. Mindful handling is needed to prevent surface abrasions.
Beyond scratch resistance, opal is generally considered to have poor to fair toughness, meaning it can be brittle. This characteristic makes it susceptible to chipping, cracking, or fracturing if subjected to sudden impacts or blows. Unlike some other gemstones that can withstand significant force, opal’s internal structure makes it less resilient to physical stress, requiring careful attention to prevent damage.
Factors Influencing Opal’s Strength
Opal is a hydrated amorphous form of silica, meaning it contains water within its structure. This natural water content typically ranges from 3% to 10% by weight for stable opals.
While opals do not “dry out” in the traditional sense, sudden or extreme changes in temperature or humidity can cause internal stress. Such environmental shifts can lead to “crazing,” which manifests as fine, spiderweb-like cracks on the opal’s surface. This occurs because the water within the opal can expand or contract at a different rate than the surrounding silica, creating tension that results in visible fractures.
The type of opal also plays a significant role in its overall robustness. Solid opals, which consist of a single, natural piece of the gemstone, are generally considered more durable than composite opals like doublets and triplets. Doublets are made by adhering a thin slice of opal to a darker backing material, while triplets add a clear, domed cap, often made of quartz or glass, over the opal layer for protection and magnification. While doublets and triplets can offer a similar visual appeal at a more accessible price, the adhesives used in their construction can be vulnerable to water or chemicals, potentially leading to separation or a cloudy appearance over time.
Caring for Opal Jewelry
Proper care is important to maintain the beauty and integrity of opal jewelry. To protect opal from scratches, it is important to store it separately from harder gemstones or other jewelry items that could cause abrasion. When not being worn, placing opal jewelry in a soft cloth pouch or a dedicated jewelry box can prevent accidental contact with other pieces.
Avoiding physical impacts is also important due to opal’s inherent brittleness. It is best to remove opal rings and other jewelry during strenuous activities, such as gardening, sports, or household chores, where they might be exposed to knocks or bumps. Even a seemingly minor impact can result in chipping or cracking the gemstone.
Opal is sensitive to extreme temperature fluctuations and harsh chemicals. Exposure to sudden changes from hot to cold, such as leaving jewelry in direct sunlight or submerging it in very hot or cold water, can induce crazing. Similarly, household cleaners, bleach, perfumes, and even chlorinated water from swimming pools can damage the opal or its setting. It is advisable to put on opal jewelry after applying perfumes or hairsprays and to remove it before swimming or cleaning.
Cleaning opal jewelry should be done gently using mild methods. A soft cloth and lukewarm water with a mild soap are generally recommended for solid opals. Gently wiping the surface or using a soft brush can help remove dirt and oils. Ultrasonic cleaners and steam cleaners should be avoided, as the vibrations or high heat can cause cracking in solid opals or damage the adhesive in doublets and triplets. For composite opals, minimal contact with water is best, and they should never be soaked.
Common Myths About Opal Strength
Several misconceptions about opal’s durability persist, often leading to unnecessary concern or improper care. One common myth suggests that opals need to be periodically soaked in water to prevent them from cracking. While opals do contain water, stable Australian opals are non-porous and do not absorb external water. Soaking them is ineffective and can actually be harmful for doublets and triplets by compromising their adhesive layers.
Another widespread belief is that opals will “dry out and die” if not kept moist. This myth stems from the understanding of opal’s water content. However, opals do not inherently dry out like organic materials; rather, rapid changes in humidity or extreme heat are what can cause the internal stress leading to crazing. The water within the opal is structurally bound, and simply exposing it to water externally does not rehydrate it in a beneficial way.
The notion that opals bring bad luck is a long-standing superstition. This folklore, sometimes attributed to a misinterpretation of a 19th-century novel, has no factual basis. Opals are treasured for their unique beauty and are considered fortunate in many cultures. Adhering to proper care guidelines, rather than superstitious beliefs, is the most effective way to ensure the longevity and vibrant appearance of opal jewelry.