Many wonder if green obsidian is natural or artificial, especially given the vibrant pieces often sold. While a subtle, natural green obsidian does exist, it is exceptionally rare. The vast majority of brightly colored “green obsidian” available in the market is, in fact, man-made glass.
The Nature of Obsidian and Its Colors
Obsidian is a natural volcanic glass formed when molten lava rapidly cools with minimal crystal growth. This rapid cooling occurs when silica-rich lava contacts cooler air or water, preventing atoms from arranging into a crystalline structure.
The color of obsidian typically varies based on the presence of impurities or trace elements within the volcanic glass. Pure obsidian is usually dark, often jet black, due to the presence of iron and other transition elements, often as magnetite nanoinclusions. Other common natural colors include brown, red, or mahogany, which often result from iron oxides like hematite or limonite. Sheen effects, such as golden or rainbow iridescence, are caused by microscopic gas bubbles stretched flat within the glass or by inclusions of nanoparticles that interfere with light.
True Green Obsidian: Rarity and Formation
Naturally occurring green obsidian is exceptionally rare and differs significantly from the vivid green glass often sold. This subtle green hue in genuine obsidian is typically caused by trace amounts of specific elements, such as iron, chromium, or magnesium, incorporated into the lava during its rapid cooling. Inclusions of minerals like chlorite or serpentine can also contribute to the green coloration.
The natural green is often a deep, mossy shade that might appear almost black in some lighting conditions, only revealing its green tint when thin pieces are held against a strong light source. Its formation requires specific geological conditions, including particular lava compositions and rapid cooling rates.
Common Materials Marketed as “Green Obsidian”
Bright, uniformly colored green “obsidian” is almost always man-made glass, often referred to as slag glass or cullet. These materials are produced by melting various raw components, including silica, and adding colorants to achieve the desired hue.
Manufacturers often create these glass pieces to mimic the appearance of natural obsidian, capitalizing on its glassy luster and conchoidal fracture. Their artificial nature allows for intense, consistent colors uncharacteristic of genuine green obsidian. Some manufactured glasses are sold under specific trade names, such as “Gaia Stone,” despite not being natural stones.
Distinguishing Genuine from Imitation
Distinguishing genuine green obsidian from imitations involves observing several characteristics. Natural green obsidian typically exhibits a deep, often subtle, mossy green color that can look nearly black unless held up to light. In contrast, artificial green glass frequently displays an unnaturally bright, uniform, or vibrant green hue.
Examining inclusions and bubbles can provide further clues. Man-made glass often contains spherical air bubbles. Natural obsidian, if it contains bubbles, typically has elongated or stretched bubbles, or they are extremely small. Natural obsidian might also show mineral inclusions, such as microlites or small white cristobalite “snowflakes,” which are absent in most artificial glass.
While both natural obsidian and artificial glass break with a conchoidal (shell-like) fracture, the overall clarity and transparency can differ. A completely transparent piece is likely not genuine obsidian; natural obsidian is translucent, allowing some light to pass through. Finally, consider the source and price; unusually low prices or questionable sellers can indicate imitation materials.