I bought a nice little Japanese book (translated to English) by Bunpei Yorifuji called ‘Wonderful Life with the Elements’. In the first few pages he gives an overview of how mankind learned to extract and use more and more elements from the earth’s crust. The universe is made mostly of hydrogen and helium, but Earth (by mass) is made of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%); with the remaining 1.2% consisting of trace amounts of other elements.