Is Obsidian Intrusive Or Extrusive?

Last Updated on July 14, 2022

Obsidian is an igneous rock, and it has a beautiful property and appearance. That is why many people use this material for their jewelry and other things. However, obsidian is an extrusive rock, and there is a reason why that is the case

If you want to know whether obsidian is intrusive or extrusive, you have come to the right place. Here is your complete guide to understanding everything about the beautiful obsidian rock. 

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Is Obsidian Intrusive Or Extrusive?

It is an extrusive rock because it is created when magma erupts from the volcano and cools down. On the other hand, intrusive rocks are ones that are formed from the magma under the ground and don’t erupt. The appearance of the obsidian rock is that of natural black glass, which is why it is also known as volcanic glass. 

Because obsidian is an extrusive rock, it will also be more fine-grained and have a lack of crystal growth. As the lava erupts and cools down, it forms obsidian in its wake. However, the cooling process happens so fast that there is no chance for the crystals to form. 

That is why obsidian has a uniform and smooth structure. As you hold the rock, you will love how smooth it feels on your hands, despite the extensive process of eruption and cooling. 

What Is The Composition Of Obsidian?

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Besides knowing if the rock is intrusive or extrusive, you must also know the composition of obsidian. For example, obsidian consists of 70% or more silicon dioxide (non-crystallized silica). That is why you will find that it is similar in its chemical structure to rhyolite and granite. 

These rocks were also originally molten, which is why they are similar to obsidian in their chemical nature. However, all of these stones have different uses, as granite is mostly used for décor in homes and offices. 

Is Obsidian A Crystal Or Stone?

Many people confuse obsidian with a crystal, but that is not the case. That is because obsidian is a stone. It forms when the molten lava cools down after a volcanic eruption. 

As the lava cools down, there is no time for it to crystallize. That means it will solidify as quickly as possible with an extensive range of trace rocks and minerals. Because of this, obsidian is a rock and is known to be a volcanic glass instead of a crystal. 

How Do You Identify Obsidian?

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One of the best ways to identify obsidian is through its appearance and presence. That is because this rock will have an excellent appearance of smooth glass. In addition, it is a rock that is a frozen liquid that might also contain traces of other minerals and rocks. 

The color of pure obsidian will be dark, but there are rare occasions where it has a white color. Most obsidian comes in black color, and that is what you will see the most in markets. If you don’t know what you have, you can also take the rock to a professional so that they can assess it. 

Is Pumice Intrusive Or Extrusive?

Now that you know about obsidian, you might wonder if pumice is intrusive or extrusive rock. Even pumice is extrusive, just like obsidian. It is produced when lava with very high water content and gases is discharged from a volcano eruption. 

When it is discharged, it is completely liquid, and it cools down rapidly. Because of this, it doesn’t have time to crystallize, which is why it is a rock. The rock also has translucent and thin bubbles that you will notice once you have this rock in your hands. 

Is Granite Intrusive Or Extrusive?

Granite is intrusive igneous rock. That is because it is formed by the cooling of magma at depth inside the Earth’s crust. Because of this, it is an intrusive rock, but its chemical structure is a little similar to obsidian. 

The magma in the Earth’s crust cools down slowly, which is where the granite forms. Its primary composition includes mica, feldspar, and mineral quartz. Granite has many uses, and you can even use it in your home or office as tiling or for décor. 

Mostly, this material is used for countertops and other home décor items. However, if you are looking for rocks to make your home look fantastic, then you can keep granite as a choice. There are many types of granites you will find that will suit the aesthetic of your home in no time. 

Jackie Palmer is a Houston-based coin journalist and fashion enthusiast. She joined Jewels Advisor’s content team after years of experience as a content strategist, managing blogs and social channels for local stores. Jackie mostly collects and studies US coins produced during the 20th century and over the years, published hundreds of articles for multiple coin publications.