The Viral Cookie Monster Agate and How Agates Form (GeoShort)

02.11.2021 - By PlanetGeo: The Geology Podcast

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Have you seen the viral "cookie monster agate"?  If not, check it out via the link below (or our instagram: @planetgeocast)! 

Both Chris and Jesse have had this viral agate image shared with them, and today we discuss how agates are formed, and how the represent a really cool and important geologic process; fluid flow!  

Agate is a form of microcrystalline silica (like quartz) that often forms from super-saturated fluid.  These fluids flow through many parts of the Earth's crust, including through small gaps or cavities in volcanic or sedimentary rocks.  The super saturated fluids will deposit agate (or calcite or other minerals) within cavities and they are deposited in concentric rings that grew much like tree rings grow! The different rings can have slightly different colors due to small impurities in the minerals that are being deposited.  

However, beware!  Agate is a porous material so synthetic dyes can be easily applied to natural agates, turning them to very showing, but artificial, colors.  In fact, most pink or bright blue agates are actually dyed.  

Listen to our GeoShort to learn about the Cookie Monster Agate!
- rockhounds
- rock collecting
- geology in the field
- agates and geodes

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