Water opals are a captivating and distinct variety of opal, known for their unique visual characteristics and how light interacts with their structure. Their clear appearance and internal flashes of color make them sought-after gemstones.
What Makes a Water Opal Unique
A water opal is characterized by its transparent or semi-transparent body, often appearing colorless or with a very light background. This clarity allows the internal play-of-color to be observed with remarkable depth, distinguishing it from opaque varieties like white or black opal.
Water opals are composed of hydrated amorphous silica, which is silicon dioxide with 6% to 10% water molecules integrated into their structure. Some water opals are “hydrophane,” meaning they can absorb water. When a hydrophane opal absorbs water, it can temporarily become more transparent and its colors may intensify, returning to its original appearance as it dries.
Visual Properties and Appearance
The internal display of vibrant colors, known as play-of-color, is a primary feature of water opals, which appears to float within their clear body. This phenomenon arises from the diffraction of light as it passes through microscopic silica spheres arranged within the opal’s structure. The spectrum of colors can include reds, oranges, greens, blues, and purples, often appearing as iridescent flashes. These internal colors can manifest in various patterns, such as pinpoint, harlequin, or flame, adding to each gem’s individuality. The transparency of water opals enhances the visual depth of this color play.
How Water Opals Form and Where They Are Found
Water opals form from a solution of silicon dioxide and water that seeps into cracks and voids within various rock types. As the water gradually evaporates over millions of years, it leaves behind deposits of silica spheres. If these microscopic spheres are arranged in an orderly, grid-like structure, precious opal with its play-of-color is formed.
Water opals are sourced from several global locations. Significant deposits are found in Mexico, particularly in the Querétaro and Magdalena regions. Ethiopia’s Welo region is also a prominent source. Additionally, water opals are found in the Owyhee region of Oregon, USA, and in some areas of Australia, such as Lightning Ridge and Coober Pedy.
Preserving Your Water Opal’s Beauty
Water opals are relatively softer gemstones (5.5 to 6.5 on the Mohs scale) and require careful handling to maintain their appearance. They are sensitive to sudden temperature changes and susceptible to dehydration, which can lead to fine cracks known as crazing.
To clean a water opal, use mild soap in warm water and a soft cloth. Avoid harsh chemicals, bleach, abrasive cleaners, and ultrasonic or steam cleaners; their vibrations and heat can cause damage.
For storage, keep water opals away from dry heat and extreme environments. In very dry climates, storing them in a padded cloth bag with a few drops of water on cotton wool for prolonged periods can help preserve them.