Obsidian is a naturally occurring volcanic glass, formed when lava extruded from a volcano cools so rapidly that mineral crystals do not have time to grow. Genuine, naturally occurring green obsidian is exceptionally rare, which makes it a frequent target for misrepresentation using artificially colored, man-made glass. Understanding the specific geological and physical properties of the natural material is the only reliable way to confirm its authenticity.
Defining the Genuine Material
The natural green color in authentic obsidian is typically a subtle hue, not a vibrant, intense shade. This coloration is not due to a separate mineral but rather to trace amounts of iron and magnesium compounds incorporated into the glass structure. Natural green obsidian often appears nearly black until it is held up to a strong light source, where the deep green tint becomes visible.
Obsidian is classified as a mineraloid. It is primarily composed of silica, generally over 70% by weight, and its formation is characteristic of felsic lava flows. In contrast, many of the intensely colored fakes are simple manufactured glass, sometimes referred to by collectors as “slag glass,” which has been artificially saturated with coloring agents.
Visual and Optical Identification
One of the easiest initial checks is to examine the color saturation and transparency of the material. Authentic green obsidian is usually dark and translucent, revealing its green color only when very thin or when powerful light passes through it. If the material is perfectly transparent or exhibits a uniform, vibrant emerald or aqua color throughout, it is highly likely to be a man-made product.
A close inspection of internal features can reveal telling differences between real and fake glass. Genuine obsidian often contains microscopic gas bubbles, which are stretched into elongated, tube-like shapes due to the flow of the lava before it cooled. Conversely, man-made glass fakes frequently contain large, perfectly round, or spherical bubbles trapped during the manufacturing process.
The surface quality, or luster, should also be assessed, as real obsidian possesses a distinct vitreous, or glass-like, shine. While it is glassy, it should not have the overly polished, almost plastic-like sheen sometimes seen on cheap manufactured glass. The overall appearance of the natural material is one of depth and darkness, often with visible flow lines or banding on closer inspection.
Physical Property Verification
A definitive physical characteristic of true obsidian is its distinctive conchoidal fracture pattern. When a piece of obsidian is chipped or broken, the resulting surface exhibits smooth, curved, shell-like ripples that radiate outward from the point of impact. This fracture is a direct result of its amorphous, non-crystalline structure, and the edges produced are exceptionally sharp and smooth.
Another test involves comparing the density of the sample, as genuine obsidian has a specific gravity of approximately 2.4 grams per cubic centimeter. While some common soda-lime glass fakes have a similar density, a simple at-home test can still be informative. By carefully weighing the sample and then measuring the volume of water it displaces, a specific gravity calculation can be made to compare against the known range for natural obsidian.
A less scientific but still useful initial check is to feel the temperature of the material. Obsidian is a poor conductor of heat, meaning that a genuine piece will feel noticeably cold to the touch, even after being held in the hand for a short period. If the sample quickly warms up to body temperature, it suggests the presence of a material with different thermal properties, possibly a low-quality glass or plastic imitation.
Identifying Common Fakes and Market Realities
The market for green obsidian is saturated with materials sold under various misleading names. Terms like “Andara Crystal,” “Himalayan Green Obsidian,” or “Volcanic Green Glass” are frequently used to market common manufactured glass. These names often attempt to add an exotic or mystical appeal to what is essentially a colored glass product.
Genuine sources of green obsidian are geographically restricted to regions with recent volcanic activity, such as parts of Mexico, the western United States, and certain areas in Turkey. Buyers should use caution if a seller cannot name a verifiable source for the material, as this is a strong indicator of a manufactured product.
Given the scarcity of high-quality, naturally colored green obsidian, the price is a significant indicator of authenticity. If a piece of green obsidian is offered at a low price comparable to common costume jewelry or inexpensive gemstones, it is a strong sign that the material is simple manufactured glass. Authentic green obsidian commands a significantly higher price due to its rarity and genuine geological origin.