One of the defining features of obsidian’s appearance is its texture. Over enough time this causes the obsidian to lose the glassy appearance over much of its surface. The glassy texture of obsidian is very unstable, and over millions of years, the silica will reorganize itself to form radial quartz crystals that look like snowflakes. The white coloration seen in snowflake obsidian is a result of a secondary process that occurs after the obsidian’s original formation. Transparent or nearly clear obsidian is very rare, and requires an extremely silica-rich lava with little to no impurities. Pro Tip: To get a better look at the crystals in your rocks and help with identification I highly recommend picking up a good geologist’s hand lens. Rainbow obsidian (one of my favorites) is likely the result of various types of microscopic feldspar crystals aligning themselves preferentially during cooling and solidification. Other colors of obsidian are possible based on the types of impurities in the cooling lava. This variety is often referred to as ‘mahogany obsidian’ due to its resemblance to the wood of the same name. It is common for rust-red coloration to be mixed with black, giving the obsidian a splotchy appearance. Red or rust-red obsidian occurs when there are microscopic crystals of minerals like limonite or hematite. If you hold up a small flashlight behind a piece of obsidian you can see through even the darkest obsidian specimens. Even black obsidian is translucent – meaning light will pass through it. It is these impurities that give obsidian its color, and depending on their relative amounts that color can vary from location to location.īlack obsidian, which is the most common and well-known variety, occurs when there are relatively large amounts of tiny inclusions of mafic (dark) minerals like hornblende, pyroxene, and magnetite. A typical obsidian specimen contains about 70% silica, with the remainder consisting of other elements like aluminum, sodium, and oxygen. Obsidian primarily consists of silica which, given more time to crystallize, would become quartz crystals. Their differences in appearance are primarily driven by the impurities contained within the silica-rich magma at the time of formation. While all obsidian meets this general description, there is a pretty wide spectrum of obsidian that can look significantly different from one another. It’s made to help everyone from brand new hobbyists to university Geology students, and includes an eBook, digital tools, a video tutorials. Pro Tip: I have created the best rock identification system you’ll find anywhere. Obsidian is very smooth, with scoop-shaped conchoidal fractures that often result in sharp edges when broken. Inclusions of white ‘snowflakes’ are common. Obsidian is a glassy-looking, very fine-grained (aphanitic) rock that is usually black but may also be translucent, rust-red, dark green, or iridescent. So, what exactly does obsidian look like? Perhaps you have found a less common variety that doesn’t match your preconceived notion of what obsidian looks like. It can grade into other rock types, making it difficult to distinguish. However, sometimes obsidian isn’t as readily identifiable as you might think. Most people with a passing knowledge of geology are familiar with obsidian (or at least the most common variety of obsidian). I’ll walk you through how to identify obsidian, what different varieties look like, and where it can be found. While obsidian is a clearly defined rock type, there are many different varieties that can appear quite different from one another. Obsidian is made from the rapid cooling of silica-rich lava. It often displays conchoidal fracturing with very sharp edges. Obsidian is a glassy, extrusive igneous rock with a felsic composition, and is typically black in color but may also be rust-red or display whiteish ‘snowflake’ inclusions. However, identifying obsidian and its many varieties is a relatively simple process once you know what to look for. While this is generally accurate, there is a lot more intricacy and variety when it comes to obsidian which can sometimes make it more difficult to identify. When most people think of obsidian they picture a black, glassy volcanic rock. It can be found in specific locations all around the world, making it relatively accessible to collectors. It is very popular with collectors, and it has plenty of practical applications. Most people are familiar with obsidian thanks to its distinct glassy appearance.
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