Obsidian is a naturally occurring volcanic glass formed from rapidly cooled lava. Its striking appearance, often a deep, glossy black, has made it a popular material for jewelry, tools, and decorative objects for centuries. The demand and aesthetic appeal of obsidian have led to the creation of various imitations, which can sometimes be difficult to distinguish from genuine specimens. Understanding the characteristics of authentic obsidian and the common materials used to mimic it can help in verifying its originality.
Identifying Real Obsidian
Genuine obsidian exhibits a distinct glassy luster. When broken, it displays a characteristic conchoidal fracture, breaking with smooth, curved, shell-like surfaces and extremely sharp edges. This unique fracture pattern results from its amorphous, non-crystalline structure. The material feels smooth and cool to the touch, and it possesses a noticeable density.
Obsidian primarily forms in shades of black, but it can also be found in brown, green, or even red hues due to various impurities. Some varieties display natural variations such as banding, visible layers formed by differences in the lava flow. Other types, like rainbow obsidian, exhibit an iridescent sheen caused by microscopic inclusions or thin layers of magnetite. Snowflake obsidian contains white, radially clustered crystals of cristobalite, which create a speckled pattern. Thin pieces of obsidian can also show translucency when held up to a strong light source.
Materials Used to Imitate Obsidian
One of the most common materials used to imitate obsidian is manufactured glass. This artificial glass can closely resemble obsidian in appearance, but it frequently contains small, spherical air bubbles. In contrast, natural obsidian rarely contains bubbles, and if present, they are elongated or tiny. Artificial glass also has a more uniform color and texture without the natural inclusions or banding seen in obsidian.
Plastics and resins are also used to create fake obsidian, though these imitations are easier to identify. Unlike dense volcanic glass, plastic or resin pieces will feel lighter. These materials also feel warmer to the touch than obsidian and are much softer, making them susceptible to scratches. While they can mimic the glossy look of obsidian, they lack its hardness and substantial feel. Less common imitations might involve other natural stones, but manufactured glass remains the primary and most convincing imposter.
Simple Tests for Verification
A visual inspection is the first step in verifying obsidian’s authenticity. Examine the surface for the glassy luster and, if there are any chips or breaks, look for the conchoidal fracture pattern. Pay close attention to any internal bubbles; round, numerous bubbles indicate manufactured glass, whereas natural obsidian has few or none, and they are elongated. Also, look for natural inclusions, banding, or iridescence, which are signs of volcanic formation.
The weight test can provide another clue; hold the suspected obsidian and compare its weight to a known piece of glass or another similar-sized stone. Real obsidian is dense and feels substantial. A temperature test involves simply holding the piece: obsidian, being a type of glass, will feel cool to the touch and take longer to warm up compared to lighter, less dense materials like plastic.
A scratch test can also be performed with caution. Real obsidian has a Mohs hardness of approximately 5 to 5.5, meaning it can scratch common glass. Gently try to scratch an inconspicuous area of a known piece of glass with the obsidian; if it leaves a mark, it suggests obsidian. However, avoid scratching the obsidian itself to prevent damage. Finally, holding thin edges of the obsidian up to a strong light source can reveal its translucency or internal patterns like the subtle sheen in rainbow obsidian, which are signs of natural formation.