Did I get Lucky Gold Nugget in Copper Matrix

[glovas]

I took a weekend journey to the Black Hills of South Dakota on a weekend prospecting hunt and I picked up this it weighs 29.5 grams and you can clearly see copper and what appears to see gold. I scratch tested it and it looks like gold but 10k melts I am thinking it's 8k or. I will upload a scratch test of copper,nugget and a 10k ring. Help please any suggestions.
Scratch test pic Left to right. Silver Ring,Piece of Float Copper,Mystery Nugget.10k Ring, 14K Ring. Help Please. Greg

 

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[Fullpan]

My guess - got yourself a gold nugget(could be brass?)

 

[DesertNuggets]

It's a beauty! Grats!

 

[glovas]

Well a good suggestion was made so I had to follow up on it could it be brass/bronze? I took it one step further. I ran a scratch test PLEASE be the Judge.
Next question where would you go to sell it for the highest value?

 

[Jason in Enid]

It looks like a piece of brass slag that has been scrubbed with abrasive to polish the high points.