Did the northwest coast indians use coppers for?

i got this answer from a really friend, and it was right.

hope this you like it me and a special to that dude!

artists need to create a realistic interpretation so that people in general can relate to the artwork. for a common people, an artist's impression gets increased only if he can create something which would look realistic. an abstract is difficult for a common people to understand whereas if a person can draw a girl with simple pencil sketch and if that looks like a real figure then the latter will be praised more than the former.