black powder after dropping gold

[steyr223]

Hello everyone
okay here goes a second grader question
I was just a little curious why does gold become brown or black powder after you drop it and what makes the color gold to begin with

 

[Geo]

i believe its the way the light gets diffused because the gold is reflecting light at all angles. if the gold is somewhat pure, it should be a light tan color when dry. the darker it is when dry shows you it has impurities, the darker it is the more impurities it has. if you can look at the dark powder under a microscope it will look like gold.