What is Water Opal?

Water opal, also known as a jelly opal, is a type of precious opal that is characterized by its lack of body color. This means that the opal appears colorless or transparent, but it may still exhibit a play-of-color, which is an iridescent shimmer of different colors that appears to move across the surface of the stone as it is tilted in the light.

Water opals have adorned humans for centuries, with evidence of their use in jewelry dating back to ancient civilizations. Their mesmerizing beauty and unique properties continue to captivate us today.

Alternative Names for Water Opal

Water opals, known for their ethereal beauty and mesmerizing play-of-color, have several alternative names. While "jelly opal" or "angel's tears" might be popular, professional contexts call for more accuracy. For gemologists, "hyalite" or "hydrophane opal" emphasize specific properties. If mentioning origin, terms like "Mexican water opal" are acceptable. Alternatively, descriptions like "colorless precious opal" or "transparent play-of-color opal" accurately convey the gem's characteristics without informal language.

"Hydrophane" comes from the Greek words meaning "water-loving," and describes how these opals tend to absorb water.

Ethiopian water opal specimen with rainbow striped play of color
Photo: Othered Opals

Characteristics and Properties of Water Opals

Composition: Hydrated silica (SiO₂·nH₂O): Water opals are primarily composed of silicon dioxide (SiO₂), but they contain a significant amount of water molecules trapped within their structure, hence the name "water opal." This water content can range from 2% to 10% by weight.

Color: Colorless or transparent: The most defining feature of water opals is their lack of body color. They appear almost like water, with a soft, ethereal glow. However, some may exhibit faint bluish or greenish tints.

Luster: Vitreous: Similar to glass, water opals exhibit a glassy, shiny luster.

Play-of-color: Iridescent shimmer: The most prized feature of water opals is their play-of-color, a mesmerizing display of rainbow hues that appear to dance across the surface as the stone is tilted in the light. This phenomenon arises due to the diffraction of light by the microscopic silica spheres within the opal's structure.

Transparency: Translucent to transparent: Water opals can range from slightly translucent, allowing some light to pass through, to completely transparent, like clear water.

Crystal System: Amorphous: Unlike many gemstones with well-defined crystal structures, water opals lack a regular crystalline arrangement.

Streak: White: When scratched against unglazed porcelain, water opals leave a white streak.

Hardness: 5.5-6.5 on the Mohs scale: This makes them moderately hard, but they are still susceptible to scratches and damage if not handled with care.

Cleavage: None: Water opals do not have any specific direction of weakness where they tend to break.

Habits and Forms: Massive, botryoidal, stalactitic: Water opals can occur in various shapes, including massive (amorphous lumps), botryoidal (grape-like clusters), and even stalactitic (icicle-like) forms.

Density: 1.8-2.2 g/cm³: This density is slightly lower than other opals due to the presence of water.

Specific Gravity: 1.8-2.2: Similar to density, specific gravity uses water as a reference point and is numerically equivalent.

Solubility: Slightly soluble in water: While not readily dissolving, water opals can slowly lose water content over time if exposed to dry environments.

Magnetism: Non-magnetic: Water opals are not attracted to magnets.

Fluorescence: Variable: Some water opals exhibit weak fluorescence, emitting a faint greenish or yellowish glow when exposed to ultraviolet light. This property can be used to help identify and distinguish them from other gemstones.

Pleochroism: None: Water opals do not exhibit pleochroism, meaning their color does not change depending on the viewing direction.

Refractive Index: 1.45-1.46: This refractive index is relatively low compared to other gemstones, contributing to their transparency.

Inclusions: Common: Water opals often contain inclusions, such as tiny gas bubbles, mineral impurities, or fractures. These inclusions can sometimes enhance the play-of-color or add unique character to the stone.

Jelly Opal / Water Opal From Mexico

Where Are Water Opals Found

Water opals, known for their lack of body color and mesmerizing play-of-color, can be found in various locations around the world. Here are some of the most notable sources:

Mexico, Querétaro: This central Mexican state boasts the historical origin of opal mining, with deposits found in the mountain ranges of Colón, Tequisquiapan, and Ezequiel Montes. These Mexican water opals are often referred to as "Cantera opals" and have a characteristic bluish or golden internal sheen.

USA, Oregon: Water opals are also found in Oregon, particularly in the Owyhee region. These opals often showcase a soft, milky appearance and a captivating play-of-color.

Australia

Lightning Ridge: This outback town in New South Wales is renowned for its diverse opal deposits, including water opals. These Australian water opals are known for their high quality and durability, making them valuable gems.
Coober Pedy: Another iconic opal-mining town in South Australia, Coober Pedy offers a range of opals, including water opals. The Coober Pedy water opals are known for their unique characteristics and can sometimes exhibit a subtle "milky" appearance.

Ethiopia, Welo: Ethiopia has emerged as a significant source of opals in recent years, and while fire opals dominate the production, water opals are also found. These Ethiopian water opals typically exhibit a bluish or greenish tint and a moderate play-of-color.

Other Localities:

Peru: Peruvian opal, also known as blue opal, is a unique variety with a semi-opaque to opaque blue-green color and is often found in the Owyhee region.

Slovakia: Water opals can also be found in limited quantities in Slovakia.

It's important to note that the specific characteristics and quality of water opals can vary significantly depending on their location. Some regions are known for producing opals with a more pronounced play-of-color, while others may yield stones with a more subtle shimmer or milky appearance. The value of water opals is also influenced by their size, clarity, and the intensity of their play-of-color.

Water Opal from Oregon

Water Opal FAQ

Are water opals valuable?

Water opals generally have less intense play-of-color and body color compared to other varieties like fire opals, resulting in lower value. However, high-quality water opals with exceptional play-of-color can still be quite valuable, offering a beautiful and affordable alternative.

Are water opals fragile?

Yes, they are relatively delicate. Avoid harsh chemicals, sudden temperature changes, and scratches.

How to clean water opals?

Use lukewarm water and mild soap, gently wiping with a soft cloth. Avoid harsh cleaners and ultrasonic cleaners.

How much does a water opal cost?

Prices vary widely depending on size, clarity, and play-of-color intensity. They can range from tens to hundreds or even thousands of dollars.

How to store water opals?

Store them in a cool, dark place with moderate humidity. Avoid direct sunlight and extreme temperatures. Wrapping them in a soft cloth for added protection is recommended.

Water Opal

Conclusion

Overall, water opals are unique and beautiful gemstones that offer a captivating play-of-color and a soft, ethereal aesthetic. While they may not be as valuable as some other types of opals, their unique beauty and affordability make them a popular choice for jewelry and other decorative items.