Agates, Jaspers, Chalcedony, Chert, Opal - How To Tell The Difference

Agates, Jaspers, Chalcedony, Chert, and Opal have many similar characteristics and similar chemical structure. Even seasoned rock identifiers struggle at times with how to label and differentiate between these rocks. And sometimes a single rock may have agate banding, jasper outer layer, and a clear quart center; making it all three! And then there is that allusive Opal. Sharing the same silica based chemical structure, but with an added water molecule or two or three, it is softer and less lustrous. But it is closely related to the others and can look a lot like jasper or chert.
In this video, Shadow and I gather some rocks near a campground near Jacob's Lake, Arizona. We were on our way to Phoenix to visit family. We also took note of the surrounding geology which included a lot of calcite, limestone, malachite, and similar rocks to the rocks we gathered. Initially, I thought we found Opal. We took them home to test them.
Testing the rocks with hydrochloric acid ruled out that they were calcite based. Testing for hardness which placed them at a 7.5 on the Mohs scale ruled out that they were opal. Taking into consideration the calcite rich geology around the area, and the overall appearance of the rocks, I concluded that they are mostly chert with some Jasper. Maybe all chert.
Shadow and I welcome your comments to help us identify these rocks. Are they chert? Jasper? Something else?
We hope our adventure and testing these rocks might help others in learning to identify rocks. And, as always, we had fun! We hope you enjoy this video and subscribe and join us on future Adventures of Shadow.

[@jimedgar6789]

Astronomy and rocks, two best hobbies.

[@adventuresofshadowdog]

Agree 100%! Thanks for watching and leaving a comment!

[@Colleen858]

I like to make up words too. Thanks for taking me along today with you and Shadow❤

[@adventuresofshadowdog]

Hahaha! Right! I just googled and learned that the latest Oxford English Dictionary has 171,465 words in it. That’s just not enough! Lol.

[@TimT-um6rt]

Thanks for helping me determine some whitish bone
Colored rock that seems to have good lapidary features!
I'm a hobby turquoise miner in Nev. and enjoy hounding a round my claim!
Anyway the rock mentioned seems to be a white chert! The lapidary characteristics
for me are more important than absolutely i.d.ing the stone!
With that being said,I still like to know as much as I can about the material I work
with.
Keep on licking rocks!

[@adventuresofshadowdog]

Thanks for watching and the interesting comment. I would love to know more about your claim. Is it a turquoise claim? I was just over the border into Nevada this weekend Rockhounding. Nevada is amazing!

[@georgetheblacksmith]

The green copper rocks, most likely chrysocolla, are from local Copper mines, one about 1 1/2 miles from the lodge, the other mine several miles west. The exterior walls of the lodge are covered with the same rock.

[@adventuresofshadowdog]

Thanks for that info! And thank you for watching and commenting.

[@andreaslavin4552]

Love your new vocabulary: opaly, cherty.
That purple oral is so gorgeous. Where did you find it?
Great video of identifying rocks.
Best to you and Shadow.

[@adventuresofshadowdog]

Hey Andrea! I have to admit I did not find the purple opal. I purchased it during the gem and rock show in 2021 at Quartzite, AZ. As always, thank you so much for watching and commenting!!!

[@BonesFPV]

Hey, I've also got a dog named Shadow. She is 17 years old. Nice video - Very informative.

[@adventuresofshadowdog]

Wow! 17 years old. What breed is your Shadow?
Thanks for watching and commenting. My Shadow is wagging his tail for your Shadow!

[@BonesFPV]

@@adventuresofshadowdog she's a Shetland Sheepdog. :)

[@adventuresofshadowdog]

Shetlands are awesome dogs! Give ‘em a little scratch behind the ear for me.

[@tmi9885]

This is why you didn’t get here until midnight.

[@lisamanrique1770]

The bright blue at the parking area probably chrysocolla.

[@adventuresofshadowdog]

Thank you, Lisa! Rock identification is a team sport. Much appreciated!

[@FieldsOfGold149]

Love the idea of rock hounding and camperI do short videos I just did two video on Jasper? Hahah! Banded chert or banded Jasper. Check them out and tell me what you think? I took a trip to my home state Missouri

[@adventuresofshadowdog]

Thanks! I will check them out!

[@markdavidson9720]

The copper rocks were brought in for traffic control, not native to area, from Southern Arizona!

[@adventuresofshadowdog]

Hey Mark! That’s a long ways to haul rocks for traffic control. But I have no reason to doubt you on that. Thanks for the info!