Dust

"An individual named Adam is not the only human being made of the dust of the earth, for as Genesis 3:19 indicates, 'Dust you are and to dust you will return.' This is true of all humans, men and women. It is an archetypal feature that describes us all. It is not a statement of chemical composition nor is it describing a material process by which each and every human being is made. The dust is an archetypal feature and therefore cannot be viewed as a material ingredient. It is indicative of human destiny and mortality, and therefore is a functional comment, not a material one."—The Lost World of Genesis One, page 70

<idle musing>
Without the surrounding context, that statement might sound unsupportable, but the rest of the chapter does support it. Walton is arguing for a functional understanding of creation, not a material one (primarily). He argues that the cosmos is God's temple; more tomorrow...
</idle musing>