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.

[@charleslupica]

Thanks for sending me the link to this video. I think you nailed it on the IDs.

[@adventuresofshadowdog]

Thanks Charles. Identifying rocks is really hard sometimes. And sometimes they are a bunch of different things making it a real puzzle. I do my best but admittedly I don’t get it right all the time. But sometimes we do! Lol

[@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.

[@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!!!

[@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.

[@jimedgar6789]

Astronomy and rocks, two best hobbies.

[@adventuresofshadowdog]

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

[@dianekanady2522]

You fascinate me. You seem so knowledgeable and I too love rockhounding. I am so glad I found your videos. P.S. I live in St. George, so know exactly where you were. You made me laugh at the comment " there is no lake at Jacob's Lake". Keep up the good work!

[@adventuresofshadowdog]

Thank you so much Diane! I think everybody is fascinating when allowed to tell their story or talk about their passions. Mine just happens to be Rockhounding and Astrophotography. But when I listen to others talk about their hobbies or professions in other fields, I think they are genius! I’m sure you are fascinating! Thank you so much for watching. And for the kind compliment. 😎

[@dianekanady2522]

@adventuresofshadowdog you are more than welcome. I am just getting into astrophotography myself, but nothing like your equipment. Just a Nikon D5600 and some different lenses. I will be watching you! 👀

[@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!

[@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.

[@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!

[@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!