Abundance of aluminum in the crust is estimated to be about 8.2% of crustal mass, however this cannot be measured directly (it is estimated from the abundance of metal in the oceans). As the crust represents about 3% of the mass of the earth, and there are no more than trace amounts of aluminum elsewhere in the earth (ie mantle and core), aluminum represents about 8% * 3% = 0.25% of the total mass of the earth. Thus, the ratio of Aluminum to Earth (by mass) is about 1:40000
