Ultramafic rocks are a type of igneous rock that contains a high percentage of magnesium and iron, with low silica content. They are primarily composed of minerals like olivine and pyroxene. These rocks typically form deep within the Earth's mantle and are often brought to the surface through volcanic activity. Common examples of ultramafic rocks include peridotite and dunite. Due to their unique mineral composition, ultramafic rocks are important in studying the Earth's interior and can also be sources of valuable minerals, such as chromite and nickel.