Obsidian is a naturally occurring volcanic glass, captivating with its distinctive dark, lustrous appearance. Its smooth, reflective surface has made it a valued material throughout human history for tools and ornamentation. Given its glassy nature, many wonder how this unique material interacts with water. This article clarifies obsidian’s properties and its behavior when exposed to moisture.
Obsidian’s Volcanic Origin
Obsidian forms from the rapid cooling of viscous lava from volcanoes. This swift solidification prevents mineral crystal formation, resulting in its characteristic amorphous, glass-like structure. Its composition is typically rich in silica, usually ranging from 65% to 80% by weight. This high silica content contributes to the lava’s viscosity, facilitating its glassy texture upon cooling.
Obsidian is technically not a true mineral due to its lack of crystalline structure, classifying it instead as a mineraloid. This volcanic glass is relatively soft, with a hardness of 5 to 5.5 on the Mohs scale. The absence of defined crystal planes causes obsidian to fracture with sharp, curved edges, known as a conchoidal fracture.
How Obsidian Interacts with Water
Obsidian is largely inert and non-porous, meaning it does not readily absorb or chemically react with water. Its glassy structure makes it resistant to dissolution, differentiating it from other rocks and minerals. For short-term exposure, such as rinsing or brief submersion, obsidian is generally considered safe.
The material’s Mohs hardness, typically between 5 and 5.5, contributes to its durability in water. This prevents it from crumbling or deteriorating easily. Water does not penetrate the bulk of the stone quickly due to its low porosity. Therefore, getting obsidian wet through normal handling or cleaning will not cause immediate damage or chemical alteration.
Long-Term Water Exposure and Obsidian
While obsidian is generally stable, prolonged water exposure can lead to subtle changes. Hydration occurs when atmospheric water slowly diffuses into the freshly exposed surface of obsidian. This forms a water-rich “hydration rind” or layer, which gradually increases in depth. Archaeologists utilize this process for dating artifacts, as the layer’s thickness indicates how long a surface has been exposed.
Extended submersion, particularly in saltwater, may alter the stone’s appearance, leading to a dulling of its natural luster or even a weakening of its structure. Additionally, extreme temperature changes, such as placing obsidian directly into very hot or very cold water, can cause thermal shock due to its amorphous nature, potentially leading to brittleness or fracturing. While these effects are typically observed after very long durations or under aggressive conditions, they highlight that obsidian is not entirely impervious to its environment.
Caring for Your Obsidian
To maintain obsidian’s appearance, simple cleaning methods are effective and safe. Use lukewarm water with a few drops of mild dish soap for cleaning. Gently wipe or scrub the surface with a soft cloth or soft-bristled toothbrush, paying attention to any crevices.
After cleaning, rinse the obsidian thoroughly under running water to remove any soap residue. Promptly drying the stone with a soft, lint-free cloth helps prevent water spots or mineral deposits, which can mar its aesthetic appeal. Avoid harsh chemicals, abrasive cleaners, or ultrasonic cleaners, as these can scratch the surface or cause damage to the material.