Where is obsidian found in the world

The resulting silica-rich magma with little remaining water becomes very viscous thick and pasty obsidian magma. This magma is so viscous that sizable mineral crystals cannot grow before chilling of the magma "freezes" crystal development. Some obsidian is erupted as lava flows at the ground surface.

These surface flows are so viscous that they flow very slowly. One article I read indicated that "an ant could probably outrun an obsidian lava flow. Portions of this obsidian flow are mixed with layers of pumice, a glassy, bubble-rich, lightweight rock that develops when water vapor steam escapes rapidly from the molten glass at or near the ground surface. Sometimes obsidian of excellent quality develops as surface lava flows.

However, the best quality obsidian often forms below the ground surface around volcanic vents. Silica-rich magma squeezes into rock fractures to form layers and lenses of obsidian that are relatively free of dirt, ash and other impurities. Changes in magma composition and water content often occur during the eruption and subsurface emplacement of obsidian flows.

The high viscosity of the molten obsidian prevents effective mixing of these magmas, resulting in obsidian that is "streaked" with different layers or colors. Each of these streaks or lines may represent a distinct pulse of an obsidian eruption.

You can visualize the process that results in streaked obsidian if you consider two blobs of green and red taffy a viscous candy that are mixed together. Distinct streaks of red and green taffy result as the blobs are mixed. In the case of obsidian, the slow flow of stiff, viscous magma away from the source vent provides the mixing needed to create the layered or streaked varieties of obsidian. The "midnight lace" variety of obsidian often has incredibly contorted streaking, apparently formed as the obsidian layers were stretched and rolled with slow movement of the magma.

The various colors of obsidian are a result of several factors. Clear varieties of obsidian contain very few opaque impurities or microscopic mineral crystals. Red or brown obsidian generally results from tiny crystals or inclusions of hematite or limonite iron oxide. Abundant, microscopic crystals of minerals like magnetite, hornblende, pyroxene, plagioclase and biotite, combined with tiny fragments of rock, likely produce the jet-black varieties of obsidian. Microscopic crystals of various types of feldspars may yield the unique blue, green, purple or bronze colors associated with rainbow obsidian.

The reflectance of rainbow obsidian is likely attributed to a preferred orientation of microscopic crystals of feldspar or mica oriented along flow layers. If you thought that, you would be wrong.

Improve this answer. Gimelist Whether or not anyone has witnessed the eruption of an obsidian and I can think of reasons not to try is not so important. Yes, the volatile and SiO2 content of a melt has a significant effect on the viscosity and rate of crystallization - that's been studied in laboratory experiments.

There is much more to be learned about these lavas, but I would not characterize their origin as 'poorly understood. I remember the "obsidian paradox" being presented in my undergrad lectures and don't remember who was teaching at the time.

During my masters volcanologists talked about obsidan formation as if it wasn't particularly special. Worth nothing however that I didn't just mean humans have not see one happening -- I mean that no obsidian has been formed anywhere on the planet the last years. The most recent obsidan I know of is Newberry Caldera at years old. I am betting that Obsidian is very common around most active volcanos around the world!

Neo Neo 6, 2 2 gold badges 25 25 silver badges 58 58 bronze badges. I am by no means whatsoever, knowledgeable in Geology. There aren't too many classes in High school either , however this was nice and simplistic enough to understand.

Featured on Meta. Now live: A fully responsive profile. It is simply an unconditional piece of volcanic glass.

Obsidian solidification on earth in most instances was subaerial. Underwater volcanic glass has alternative names such as tachyllite and hyaloclastic. The volcanic glass and obsidian are therefore not synonymous, although you can often freely use both terms.

Volcano glass is an igneous rock made up of a magmatic content mainly uncrypted. Most of it is not crystallized because the crystals had two difficult problems which restricted their growth. Large crystals have to develop for a long moment. I gave a subtle indication of what might be the second issue. So obsidian forms from viscous magma only? Often yes, but not always. The structure of most obsidians is rhyolitic. The thickest lava has the largest concentration of silica.

Why does this matter? Since silica polymerizes magma. There are many bridges chemical connections between silica oxygen anions SiO2 , which is why it is so difficult to relocate this magma. If the water has many electrons cations , it is less viscous, because the frame system of silica is broken by these cations.

The chemicals hodium silica content produce a elevated viscosity that shapes a natural glass from lava when rapidly drying. The chemical composition is often discovered on the edges of rhyolitic lava flows recognized as obsidian flows. Love you guys!! Keep up the hard work! Mailee Feb 1, This is an awesome thing to learn! Karter Oct 31, I think obsidian is a rock that is needed for stuff.

Nov 1, You're right, Karter! Obsidian is still used for jewelry and for surgical purposes! Colton Oct 27, Oct 28, Hello there, Colton! Thanks for joining us at Wonderopolis! Apr 11, Nikau Mar 13, Mar 16, We're glad you liked this Wonder! Trent Jan 13, Jan 14, Welcome, Trent! Wonderopolis Mar 31, W Nov 4, What can mine obsidian?

Also my sister has blue obsidian. Wonderopolis Nov 5, Garett Oct 28, Wonderopolis Oct 29, We're not sure, Garett! If you discover the answer, we hope you'll share it with us! Peterson Oct 28, Hello there, Peterson! Thanks for joining us here in Wonderopolis!

Mckenzie Oct 28, Dear wonderoplis how does it form into it. Sincerely McKenzie. Content Oct 28, Dear wonderopilis, I never new obsidian was igneous. I learned a lot about obsidian. Maybe you should tell me about obsidians history. Sincerely conlen. John Oct 28, Brooke Oct 28, Dear Wonderopolis how sharp is Obsidian? You should compar it. Maya H. Obsidian is considered a cheap luxury item. Most gemstones are rare and expensive, but obsidian, not even a jewel, is prettier than some emeralds when made smooth!

I would wear obsidian jewelry. Thanks for a great Wonder today! A question: Is pbsidian associated with any myths or legends? It seems it could be, with its striking black color.

Tj Oct 28, Dear Wonderpolis, It's amazing that obsidian is harder than surgical steel! How does obsidian get its glassy look? I always never new that obsidian was not a full mineral.