Quartz and feldspar are the two most common minerals in the Earth's crust. Together they make up over 60% of the solid matter in the Earth's crust. Quartz is a hard, transparent to white mineral that is composed of silicon and oxygen. Feldspar is a name given to a group of minerals that are all composed of silicon, oxygen, and one or more other elements such as aluminium, potassium, and sodium. Feldspars are typically white, pink, or grey in colour.