An igneous rock that contains quartz and potassium feldspar would have a mineralogic content placing it in the range of

The answer is granitic or felsic rocks

Explanation:

Felsic is a term used in geology applied to silicate minerals, magmas and rocks, rich in light elements such as silicon, oxygen, aluminum, sodium and potassium (describs igneous rocks that are relatively rich in elements that form feldspar and quartz). This term is a combination of the words "feldspar" and "silica". Felsic minerals are generally light in color and have a specific gravity of less than 3. The most common felsic minerals are quartz, muscovite, alkaline feldspars (eg orthoclase) and feldspars from the plagioclase series. The most common felsic rock is granite. At the opposite end of the rock spectrum are mafic (rich in iron) and ultramafic (rich in magnesium) rocks and minerals.