Strange double rock or agate...Please help

sharris · Mar 24, 2021

Just wondering if anyone can help me identify this rock/agate. Obviously cut and polished and I'm pretty sure it's some sort of agate, but just curious if anyone can help with type or origin and if this double shape is common. It's about 3" tall x 4" wide and about 2 pounds. Thanks for any information!

TheCannonballGuy · Mar 24, 2021

It is a variety of agate. Yours was formed when mineral-rich groundwater deposited the minerals inside a volcanic-gas bubble. In you case, two gas bubbles which partially merged while the magma was still molten.

Most (but not nearly all) volcanic gas-bubble agates & geodes we see for sale in the US were imported from Brazil. Waaay back when I was a Rockhound & mineral collector in the early 1970s, I bought several Brazilian ones at the local "Rock & Mineral Shop" in uncut condition (sold by the pound). The shop's owner would cut them in half with his rocksaw for a small fee. Some of the results were gorgeous, and some were ho-hum.

sharris · Mar 24, 2021

TheCannonballGuy said:
It is a variety of agate. Yours was formed when mineral-rich groundwater deposited the minerals inside a volcanic-gas bubble. In you case, two gas bubbles which partially merged while the magma was still molten.

Most (but not nearly all) volcanic gas-bubble agates & geodes we see for sale in the US were imported from Brazil. Waaay back when I was a Rockhound & mineral collector in the early 1970s, I bought several Brazilian ones at the local "Rock & Mineral Shop" in uncut condition (sold by the pound). The shop's owner would cut them in half with his rocksaw for a small fee. Some of the results were gorgeous, and some were ho-hum.

WOW!!! Thank you so much CannonballGuy for ALL the great info!! That is much more in depth than I ever expected! That's why I love this website...so many knowledgeable people who are so willing to help others and share great info! Thanks again!! steve