1. Oxygen (O): It makes up about 46.6% of the Earth's crust by weight. It's found in many common minerals like quartz (silicon dioxide) and feldspar.

2. Silicon (Si): This element makes up about 27.7% of the Earth's crust by weight. It combines with oxygen to form silica, which is a major component of many rocks.

These two elements combine to form silica (SiO2), which is the foundation of many common rock-forming minerals.