Where did gold come from?





http://learningcommunity.com.br/course/c65tw
Science and Nature: The sky is Everywhere, It Begins at Our Feet


https://docs.google.com/presentation/d/1MDRbOof4FBcQvQ1CHg5_gF7dGQY0qQ0UKbIWEY1Ey9k/edit#slide=id.p