Magnesium (Mg): Magnesium can contribute to the green coloration of some obsidian varieties.Iron (Fe): Iron impurities can cause obsidian to appear brown or black.However, it can contain various impurities and trace elements that give rise to its different colors and varieties. The chemical composition of obsidian is approximately 70-75% SiO2. Obsidian is primarily composed of silicon dioxide (SiO2), which is the same chemical composition as quartz, but it has a completely different structure due to its rapid cooling from a molten state. When classifying or identifying obsidian, it’s essential to consider its color, inclusions, transparency, and geological origin to accurately describe and categorize it. It’s important to note that the classification of obsidian can vary among geologists, mineralogists, and collectors, and there are many regional and local names for different types of obsidian based on their specific appearances and geological sources. For example, obsidian knives, arrowheads, or sculptures can be classified by their intended purpose or cultural significance. Some varieties are translucent when sliced thinly and held up to the light, allowing light to pass through.Īrtistic and Cultural Classification: In the context of art or culture, obsidian objects may be classified based on their use and design. Translucency: Obsidian can be classified based on its translucency. Green Obsidian: Found in various locations, including the United States and Mexico, and known for its green coloration. Obsidian Cliff Obsidian: From Yellowstone National Park, USA, known for its black or banded appearance.Īrmenian Obsidian: From Armenia, often characterized by its brown or gray color. Obsidian Buttes Obsidian: From California, USA, known for its black color and use in tools. Different regions around the world produce unique varieties of obsidian, each with its own characteristics. Geographical Origin: Obsidian can also be classified based on its geological source. Magnetite or Hematite Inclusions: Some obsidian varieties contain tiny magnetite or hematite crystals, which can impart a metallic sheen or magnetic properties to the rock. The pumice fragments can create a textured appearance in the obsidian. Pumice Obsidian: This type of obsidian may contain small fragments of pumice stone, which is another volcanic rock. Inclusions: Obsidian can also be classified based on the types of inclusions it contains: It’s prized for its unique luster in jewelry. Gold Sheen Obsidian: Gold sheen obsidian has a shiny, golden or metallic appearance caused by the reflection of light from microscopic gas or mineral inclusions. It’s often used for tools, jewelry, and ornamental objects.
Some common color varieties include:īlack Obsidian: This is the most common type, known for its deep black color. Here are some common classifications of obsidian:Ĭolor Variations: Obsidian can be classified based on its color. Obsidian is a type of volcanic glass, and its classification primarily revolves around its physical characteristics, color variations, and any unique features or inclusions it may have. Reason, the obsidian is sometimes regarded as a mineraloid. Structural ordering similar to crystals only in very short distances. Major minerals: Amorphous volcanic glass that exhibits the The translation into English of Natural History written by Pliny the Elder of Rome shows a few sentences on the subject of a volcanic glass called obsidian (lapis obsidianus), discovered in Ethiopia by Obsidius It is ascribed to Theophrastus who used it for the first time in 320 BC. Name origin: The name obsidian is very old. It is fragile, tough and it disintegrates to very sharp slivers. Diffusion in the very viscous acid and felsic lavas with highly polymerized SiO2 tetrahedrons is slow, thus inhibiting the nucleation of crystals and supporting the origin of the glassy structure. Obsidian most frequently originates by a rapid coooling of a felsic viscous lava. Those are combination of black and brown colours. Hand-specimen rock is common combination of two colours. Colour is controlled factor by trace element content and the character of inclusion.
Also It occur red, brown-green, green, yellow and rare transparent colourless. It usually colours dark, black, grey-black to grey. Result of this formed, glass occupies more than 80 % and that have seeming conchoidal fracture and vitreous luster. It is occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes.
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