Silver cube?

[Rick624]

14.346 oz rings up silver on at pro and a fisher, non magnetic, black oxidized took a file to it and shinny like silver. What do you think?

 

[Back-of-the-boat]

Need better pictures too dark, try in sunlight.

 

[Helix]

I find chunks of rock with copper in it often. Poss that's what you have. But then I am in the Midwest were it is common.

 

[weregolf]

By white color can be lead (high grade)

 

[tamrock]

The shinny silver your seeing could be just a very thin deposit left by the steel from the file itself. Maybe try a hard non metalic grinding disc or bench grinder? But if what you say is true of the signal you get out of the MD then it very well may have metallic elements? I can't really tell anything by what I see in the photo's? Take it outside in the sunlight to photograph on a lighter colored surface. Something like a concrete patio or sidewalk may be good.

 

[Anduril]

If 50% silver, I'm thinking "$121.47" scrap value.
But that's just me.

Hope it's something good for you!