Obsidian is a naturally occurring volcanic glass formed by the rapid cooling of lava. While typically dark, certain varieties exhibit striking optical properties. Silver Sheen Obsidian is one such example, distinguished by a bright, metallic luster that appears to float just beneath the surface. This unique appearance raises the question of whether this shimmering effect is natural or a result of human manipulation. The distinctive silver sheen is a completely natural phenomenon created deep within the earth during the rock’s formation process.
The Geological Origin of Obsidian
Obsidian begins as felsic lava, meaning it is rich in lighter elements, particularly silica (often 65% to 80%). This high silica content makes the lava extremely viscous, which impedes the movement of atoms. When this lava is extruded from a volcano, it must cool very quickly upon contact with the cooler environment, such as air or water.
The rapid drop in temperature prevents the atoms from organizing into an ordered, crystalline lattice structure. Instead of forming mineral crystals, the atoms are frozen in place, resulting in an amorphous structure. This lack of true crystallization is why obsidian is classified as a volcanic glass rather than a mineral. The solidified product is a hard, brittle material that exhibits a characteristic conchoidal, or shell-like, fracture.
What Causes the Natural Silver Sheen
The silver sheen results from microscopic inclusions trapped within the glassy matrix during the rapid cooling phase. These inclusions are minute mineral particles or tiny bubbles of water vapor and gas, not large crystals. As the lava flows and cools, internal stresses stretch and flatten these inclusions along the flow lines of the viscous material.
These flattened micro-inclusions are aligned in parallel layers within the black glass. When light strikes the polished surface, it is scattered and reflected off these numerous internal layers simultaneously. This light interference produces the distinctive optical effect known as chatoyancy or aventurescence. The resulting metallic shimmer, which shifts when the stone is moved, is entirely natural.
Identifying Genuine Silver Sheen Obsidian
Because of its attractive luster, Silver Sheen Obsidian is sometimes imitated by treating industrial glass or coating low-quality material. A key indicator of genuineness is how the reflective sheen interacts with light. Natural sheen obsidian displays an iridescence that appears to move and change intensity as the viewing angle shifts.
The metallic effect in genuine Silver Sheen Obsidian seems to originate from within the stone, often appearing three-dimensional. Imitations, such as those with a painted or coated surface, show a flat, static reflection lacking the same depth. Genuine material, sourced from volcanic regions like Mexico and parts of the United States, also possesses a specific density and hardness. Observing the movement of the light across the stone, looking for that internal, shifting reflection, is the best way to ensure authenticity.