1st - I noticed this was your very first post - so, Welcome Aboard JuanTomm! You didn't list your state (or country) in your profile. So, you might consider jumping over to Sub-Forums: Select Your Area.... and selecting location information (i.e., clubs, hunts, finds, legends, maps, etc.) directly related to your state (or country).
2nd - I moved from What is it? over to Forum: Rocks/Gems for more exposure.
Probably some kind of superficial copper oxidation or copper carbonate especially considering where it was found. Pics in natural light that aren't blurry and a close up would help