Clinker

So all metallic colors throughout the rocks have absolutely no types of gold?

I live in a place where the rocks that look like this are as big as houses! 

Unfortunately, gold does not usually occur in sedimentary rocks like coal.  So, clinker is mainly silica.  Think sand and dust that washed and blew into the marshes that eventually turned into coal.

There is one type of gold deposit in sedimentary rocks, the "fossil placer."  Whis is where an ancient stream had gold washed into it from an igneous or metamorphic source and was then buried and turned into sandstone. 

"By hammer and hand all arts do stand."