ooookkkkkk Bulgaria looks alot like california......if gold has been found in the area well..... you will find more.so the Mariposa formation wich is what the Motherlode in california is is a series of lodes, veins intrusions that filled fissures in metamorphic rock.... meaning you will find quartz veins sandwiched between schist, slate, greenstone, serpentine.....black..white...black...Ma natures awesome oreo cookie and oh do you wanna pay attention to the cream in the middle.....where did the nugget come from? Quartz with any mineraliztion especially pyrite is a very good thing...yes look for rusty quarts....but, especially look for rust and mineraliztion at the contact zones where the quarts and metamorphic rock touch...if your in a gold bearing area id say with certainty within feet of where your pics were taken all those rough spots, quartz veins,etc have gold in them its just microscopic. if its in sulfides you will have to process tons to even see an ounce......if its free milling gold you could find it in placer form in that rough crazy bedrock.........look up the local mining history and try to find some geology reports good luck.