Any rock experts here?

[basilone0331]

This is a rock I dug up about 10 years ago in my parents backyard in Sandy. It was about 7-8 feet down in a layer of sand. It has what appears to be some type of a imprint on the outside in the basic shape of a wing, on the other side is a somewhat spherical shape of a different material than the outer rock. There is a small chip in it from when I struck it with the shovel, other than that it is in the same shape as I found it in. Any ideas?

[rockgremlin]

Why were you digging down 6 feet? Did you kill somebody? :lol8:

It's difficult to ID rocks and minerals from pictures. Much easier to do in person. Look closely at the clump of material that is different from the outer rock. Does it have a grainy texture like a sandstone or siltstone? Does it have any other defining texture to it? It could be some sort of fossil, or it could just be a blob of sandstone that is more resistant to erosion than the outer rock.

[Udink]

Yeah, what Rock said. :) It's hard to tell from pictures, and I'm no expert, but the dark impression on the smooth side looks like a fossil of some sort, possibly something as simple as some jumbled plant matter, or maybe some small sea creature (cephalopod or crustacean?). The knobby thing on the other side looks more like a concretion, what rockgremlin described as simply rock that's more erosion-resistant than the rest. Sometimes concretions form around the fossilized remains of plants or animals, so it's definitely plausible that the dark impression on the one side is from something that was once alive.

[basilone0331]

Why were you digging down 6 feet? Did you kill somebody? :lol8:
No comment.

Look closely at the clump of material that is different from the outer rock. Does it have a grainy texture like a sandstone or siltstone? Does it have any other defining texture to it? It could be some sort of fossil, or it could just be a blob of sandstone that is more resistant to erosion than the outer rock.
The inner part looks like clay with a few bands of white material in it. On the outer part around the impression it has small ripples that are in the shape of the "wing".

[rockgremlin]

Since you live in Sandy, that rock most definitely washed down into the valley from large runoff events that occurred when the glaciers up Big and Little Cottonwood Canyons melted at the end of the last Ice Age. The fact that it is smooth and well rounded indicates that it has undergone erosion from being tumbled on the bottom of a river or stream.

Without seeing it in person, if I had to wager a guess, I would probably say that it is a concretion.

[Sombeech]

Any rock experts here?

Yeah, I'm a huge 80's metal fan, I lov--- oh, oops.

[asdf]

sorry to change the subject
do you have any idea what this could be?

http://farm1.static.flickr.com/166/382144797_48bcc4e5b5.jpg

[JP]

Any ideas?
Not quite the rock I'm used to seeing :roflol: