How is an Obsidian Formed?

Obsidian is a naturally emerging volcanic glass formed while lava extruded from a volcano cools rapidly with minimal crystal increase. It is an igneous rock.

Across History, Obsidian has been used to make guns, tools, equipment, ornaments, and mirrors. But, because of its conchoidal fracture (clean curved surfaces and sharp edges), the sharpest stone artifacts have been usual from Obsidian.

Let us study the Comprehensive Guide on the formation of Obsidian. 

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Process of Obsidian Formation


An Obsidian is usually an extrusive rock that solidifies above the earth’s surface. However, it may form in a spread of cooling environments: alongside the rims of a lava float (extrusive) along the edges of a volcanic dome (extrusive)

The size of the crystals of minerals making up an igneous rock, in general, rely upon the time it took for the supply magma to chill (there may be different elements, along with crystals being resorbed due to adjustments within the magma’s physical and chemical properties, but we will ignore those for the motive of this question). If magma is allowed to cool very slowly, the crystals have time to grow, now and then getting quite massive. 

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Gabbro-Intrusive Rock

These coarse-grained rocks are generally intrusive, meaning they cool underground, so their heat energy is misplaced very slowly to the encompassing rock. The intrusive rock called gabbro is an example of this; it essentially has the identical chemistry and mineralogy of basalt but is a great deal coarser-grained as it cooled slowly.

As that means, if a magma cools more quickly, the crystals have much less time to develop, so they cease a whole lot smaller. Basaltic magma that receives erupted onto the surface loses its head in no time, so as opposed to the coarse-grained rock referred to as gabbro, we end with the plenty finer-grained rock referred to as basalt.

Cooling of Magma

cooling of magma

If we consider this as a logical conclusion, then rapidly cooling magma—for example, by using chilling it in a medium on the way to bring away its warmth in no time, inclusive of water—can reason the magma to solidify while the crystals are nevertheless tiny, or earlier than they can even, in reality, begin to shape at all.

In this situation, the magma is “frozen” into what amounts to glass—a largely disorderly collection of molecules with little or no crystalline shape in any respect. 

Glassy Structure 

glassy structure

It’s well worth noting that Obsidian, like all glass, is “metastable”…that is, it’s a better-energy state for the molecules composing it.

Since entropy says that matters in nature typically try and enter the bottom energy country feasible (for example, cliffs generally tend to slump, through landslides, into sloping piles of rock), the disorderly, glass state of Obsidian gained won’t last, both, over time, the molecules will begin to arrange themselves into decrease-strength, extra stable crystalline lattices. 

In other phrases, the Obsidian will crystallize, becoming an utterly best-grained rock instead of glass. This occurs very slowly in our terms; however, it quickly occurs in geological expressions. Obsidian is, consequently, a quite ephemeral geological element!

Obsidian is an extrusive igneous rock. It is happening as a herbal glass fashioned with the rapid cooling of viscous lava from volcanoes. This shaped glass occupies more than 80 % and has to seem conchoidal fracture and a vitreous luster.

Various Colors

Various colors-Obsidian

It usually colorations dark, black, grey-black to gray. Also, It occurs pink, brown-green, inexperienced, yellow, and rare obvious colorless. Colour is a controlled element using trace element surface and inclusion character.

Hand-specimen rock is a combination of 2 colors. Those are a mixture of black and brown colorings. Obsidian maximum regularly originates using rapid cooling of felsic viscous lava.

Diffusion within the very dense acid and felsic lavas with exceedingly polymerized SiO2 tetrahedrons is sluggish, as a consequence inhibiting the nucleation of crystals and supporting the origin of the glassy structure. It is fragile, complex and it disintegrates to very sharp slivers.

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Classification of Obsidian


Volcanic rocks containing more than 80% of glass no longer have their classification, but they may be characterized using the TAS diagram in phrases in their chemical composition. However, individual varieties of volcanic glasses also fluctuate in their shape and texture phrases.

Air bubbles that might be imparted in the route of magma waft are aligned in a regular pattern in some types. For example, sheen obsidian has golden results, even as rainbow obsidian possesses function rainbow luster. Another not unusual black kind is snowflake obsidian, which has tiny white crystals.

What type of Rock is Obsidian?

Most people assume that Obsidian, igneous rock from melted rock or magma. However, Obsidian is an “extrusive” rock; it’s made from magma that erupted out of a volcano. If it was an igneous rock shaped from magma underground and did no longer erupt, it might have been referred to as an “intrusive” rock.

How is an Obsidian Crystal formed?

Obsidian is an igneous rock occurring as a natural glass shaped using the speedy cooling of viscous lava from volcanoes. Obsidian is extremely rich in silica (approximately 65 to 80%), low in the water, and has a chemical composition similar to rhyolite.

How is Obsidian formed inside the rock?

Increased viscosity impedes crystallization, and the lava solidifies as a pitcher. Obsidian boulders shaped from lava glide.

What rock cycle is Obsidian?

Obsidian, or volcanic glass, cools so fast which you can’t see any crystals at all! Instead, igneous rocks shape while magma or lava cools down and turn from liquid to strong. When this occurs, igneous rocks shape crystals and are said to crystallize.

Where to Find Obsidian?

Obsidian is found in lots of places worldwide. However, it is confined to areas of geologically recent volcanic activity. It is older than some million years and is rare because the glassy rock is rapidly destroyed or altered by weathering, warmness, or other processes.

Significant deposits of Obsidian are located in Argentina, Canada, Chile, Ecuador, Greece, Guatemala, Hungary, Iceland, Indonesia, Italy, Japan, Kenya, Mexico, New Zealand, Peru, Russia, United States, and many different locations.

Obsidians may be found all over the globe in regions with volcanic explosions. For example, giant deposits of Obsidian can be found within the United States, Canada, Mexico, Guatemala, Argentina, Chile, Greece, Hungary, Italy, Iceland, Russia, New Zealand, Japan, and Kenya.

How is Obsidian Gathered?

One of the best approaches to obtaining Obsidian is to discover a lava pool and pour water on it, after which mine with a diamond pickaxe. Likewise, on occasion, it is possible to locate lava pools that have been evidently converted to Obsidian via waterfalls. When mining this way, the pinnacle layer of Obsidian typically has lava beneath it.

What minerals are Obsidian a product of?

Abundant, microscopic crystals of minerals like magnetite, hornblende pyroxene, plagioclase, and biotite, mixed with tiny fragments of rock, possibly produce the jet-black varieties of Obsidian.

Another frequently searched question is Black Obsidian vs Black Tourmaline, to know click here.

Final Thoughts

Obsidian Formation-Quick Look

Obsidian formation


Obsidian is produced from volcanoes, while felsic lava cools and freezes without sufficient crystal increase. It is usually determined in regions where the cooling of lava became rapid—including on the margins of the lava flows and in places in which the lava entered a lake or sea. As silicate-wealthy magma extrudes from in the earth’s crust, it falls over the water our bodies or different surfaces in touch with water.

As a result, the lava gets cooled and consolidated immediately without crystallization. Hence, Obsidian can not be categorized underneath any crystal machine. Instead, this glassy rock is metastable—over the years, it turns into pleasant-grained mineral crystals.

Obsidian no longer has crystals because it forms from felsic lava, which is high in silica. The magnetic properties of Obsidian had been recognized by way of geologists for some time, and this was a bit challenging task to do research.

Obsidian is marked via its absence of crystals. Because crystals cannot shape in this example, the lava cools right into a volcanic glass containing no crystals! Obsidian is mineral-like but no longer an essential mineral because, like glass, it is not crystalline; further, its composition is too complicated to incorporate a single mineral.

Obsidian is frozen lava – fashioned after cooling while sure natural molten rock is poured out of a volcano into the air and solidifies. While Obsidian is not used to construct indestructible partitions or portals, it makes surgical equipment.

Obsidian is likewise called “nature’s glass” due to its glassy appearance. When Obsidian breaks, the fractures are very sharp, which is why they changed into used as tools within the Stone Age. Seventy percent of obsidian rock is a product of silica. As a result, Obsidians can only form near active volcanos.

We hope you understood how Obsidian is formed in an elaborated way in this post. We want you to share this article and spread your love.