Ask-A-Geologist #8: What is obsidian rock used for?

What is obsidian used for?

Hi everyone! We have another fabulous Ask-a-Geologist question from one of our readers. Today’s question is about obsidian rock and its uses. This is one of our favorite igneous rocks so let’s jump into the the question and answer.

What is obsidian rock used for?

Hi John!  In ancient times, obsidian rock was used to make crude knives and tools. Today, obsidian is used in the production of rock wool, knives, and jewelry.

Obsidian Igneous Rock

There are two types of obsidian that might interest you. There is the standard, solid black obsidian and then there is snowflake obsidian. Obsidian is an extrusive igneous rock meaning that it forms outside the volcano. When the magma is ejected from the volcano, it cools so quickly that it forms a black glass, which is obsidian. This rock has a conchoidal fracture and is very shiny.

Snowflake Obsidian Igneous Rock

Snowflake obsidian is actually the same as black obsidian; however, it has areas that have started to break down. When the mineral breaks down, it forms these white areas that form in the shape of snowflakes, which is why they call this snowflake obsidian. This process is called devitrification and the white spots are actually the mineral cristobalite, which is a form of quartz.

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