Open me up to find either an organ or gold. Confident? Then say it with this too

I have a spine, but no bones to bear, Pages I hold, a story to share. With lines to fill, or sketches to make, What am I, for goodness sake?

Holding dessert, directing traffic, or frustrating a recovering dog, What am I?

I hold a bright rainbow right in your hand. I am not a crystal, I am soft and I glow, I catch every color the sunlight can throw.

An early human cousin once had me, And I've been relied on ever since, Mounted on a mast I've toured the seas, And together we harness the winds