What causes this type of toning?

I found this in a cull bag and in the bag it just looked like gross black tone, but fortunately I took it out and when it was in the light it showed all this rainbow coloring. Got me wondering what caused this as (and I’m new) I usually see black OR color toning, not both. (It’s a 64D ... obverse is normal.. nice but zero tone)

Thank you!

 

Log in or Sign up to hide this ad.

Terminal state with room for redemption.......

 

I'd soak it in some acetone, rinse it with distilled water, place it upright to allow it to dry, and then put it a plastic baggy, with all of the air squeezed out, to preserve it.......

 

Check for the Type C reverse. As for the toning, IDK but I would guess some type of gas.

 

Many dark coins have color that's tough to see. The lighting and angle bring out any color that is there.

 

The colors look right for some late stage toning; probably exposed to moisture, heat, some source of sulphur fumes.

 

So is the black bad, or just fine / ugly?

 

I'd leave as is. Lots of collectors like that type of toning.