Need help with an ID

[brandon_insd 0]

I need some help with an ID for a find that I picked up in the foothills of San Diego. It was embedded in a much larger rock and covered in loamy soil. It also has a greasy feel to it. Thanks.

[d_day 359]

I’m going to guess that this is some sort of industrial byproduct. 

[Stillweaver hillbelli 348]

Where in San Dago and what sort of rock found in?I'm familiar w/ most parts, areas, rock,soil types in the county, aswell as old mining sites. Lived here over 50 yrs...and studied the geology.

Do a streak test on back of toilet lid, try to scratch it with  a knife.   Could be slag or remnant molten glass.

[Stillweaver hillbelli 348]

11 hours ago, d_day said:

I’m going to guess that this is some sort of industrial byproduct. 

Or melted beer bottles from an old bonfire.

[Bedrock Bob 4,192]

I think that is a hunk of polyester or epoxy resin.

Check out the lint and cat hair clinging to the surface. The burnished corners and flow lines on the surface. I don't think it is mineral at all. And it definitely is not glass, silica or some sort of slag. The surface is completely wrong for that and it is going to be much softer. Silica would have conchoidal chips along those sharp edges. This thing is all burnished and polished on the surface. It has no tiny Hertzian cone shaped chips and flakes that would indicate a silicified material.

The "greasy" feel is the clincher. It is a polymer of some sort.

The material on the surface seems to be "stuck to" the piece rather than formed along side of it. It looks a whole lot like clay based kitty litter. That is a very popular material to support molds when casting in glass and resin. The waste or spillage often winds up on a bed of kitty litter and then picked out and thrown away after it solidifies. Could that be the case here?

Whittle on it a bit with a knife or file. That will give you an idea of hardness and what the chips or shavings look like. My guess is that it is a whole lot softer than you would expect it to be. Maybe get it hot on a corner and observe the results. I think you will find this is manufacturing waste of some sort.

[brandon_insd 0]

It was found on private land in an undeveloped area within the Singing Hills area of San Diego. Someone would have to go through a lot of effort to dump some sort of production byproduct in this area. The material clinging to it is sand and paper towel from my wife trying to clean it off. It was able to scratch with a knife. Also, you cant really tell by the photos but it is semi translucent.  

[Stillweaver hillbelli 348]

People burned trash all the time, back in the day,  maybe old carpeting or other plastic. See if it burns under a torch flame.

River bottom singing Hills or DG and boulders? Near any houses or old foundations,outbuildings?

[Diggingd 36]

Hmmmm definetly a weird find, I think I have to side with Bob on this one it looks to be more of a resin based object with its sticky and greasy properties, I'd try putting it into a fire pit and try lighting an edge or a small piece of it (just in case it is highly flammable itll be in a safe environment) and I dont think this is worth anything, but if it's byproduct of something there could maybe be hidden treasure just lying around that boulder could be worth it to go check it back out and it wouldnt hurt to get a picture of the rock it was embedded in to maybe change our opinions on what it might be.