Understanding Opal Hardness and Its Implications
Updated: Sep 25
Opal is a captivating gemstone known for its stunning play of colors, known as opalescence. However, its beauty is paired with a delicate nature, making it one of the softer gemstones used in jewelry. This post explores the hardness of opal, the factors influencing its durability, and how to care for opal jewelry to preserve its brilliance.
What Determines Opal's Hardness?
Mohs Hardness Scale
Opal ranks between 5.5 and 6.5 on the Mohs scale of hardness, indicating that it is relatively soft compared to other gemstones like quartz or sapphire (GIA Catalog) (gemcollectorz.com). This softness means that opal is susceptible to scratches from harder materials and requires careful handling.
Factors Influencing Hardness
Composition and Water Content: Opal is composed primarily of hydrated silica, with water content ranging from 3% to 20%. Higher water content tends to make opal softer, while lower water content can increase its hardness (Geology Science) (gemcollectorz.com).
Silica Sphere Size and Arrangement: The size and arrangement of silica spheres within the opal affect its hardness. Smaller, tightly packed spheres result in a harder structure, whereas larger spheres make opal more fragile (gemcollectorz.com) (gemcollectorz.com).
Type of Opal: Precious opals, which exhibit a play of color, are generally harder than common opals due to their more ordered internal structure (gemcollectorz.com) (Geology Science).
Caring for Opal Jewelry
To maintain the beauty of opal jewelry, it is essential to follow proper care guidelines:
Avoid Harsh Chemicals: Keep opal away from harsh chemicals like bleach and ammonia, which can damage its surface (gemcollectorz.com).
Store Properly: When not in use, store opal jewelry in a soft, lined box or pouch to prevent scratches. Keep it away from harder gemstones (gemcollectorz.com) (Geology Science).
Clean Gently: Use a mild detergent and lukewarm water to clean opal jewelry. Avoid abrasive cleaners and ultrasonic machines, which can harm the gemstone (gemcollectorz.com) (GIA Catalog).
Protect from Heat: Avoid exposing opal to excessive heat or direct sunlight, which can cause cracking or discoloration (Geology Science).
Applications and Value
Despite its relative softness, opal is a popular choice for jewelry, especially in rings, pendants, and earrings. Its unique play of colors makes it an eye-catching gemstone. Opals are also used in ornamental objects and are believed to have healing properties that promote emotional balance and creativity (gemcollectorz.com).
Opal's value is influenced by factors such as color, clarity, pattern, and carat weight. Precious opals with vibrant play-of-color are particularly sought after by collectors (gemcollectorz.com).
Conclusion
While opal may not be the hardest gemstone, its captivating beauty and unique characteristics make it a prized possession. With proper care and maintenance, opal jewelry can be enjoyed for generations, offering a glimpse into the enchanting world of gemstones.
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