Igneous rocks are formed when molten rock, known as MAGMA, cools and solidifies. MAGMA is a hot, liquid or semi-liquid material found beneath the Earth's surface. Igneous rocks are the most abundant type of rock on Earth and can be found in many different shapes and sizes. They are composed of minerals such as quartz, feldspar, mica, and hornblende. Igneous rocks are used in construction, landscaping, and for decorative purposes.