Here's why:
* Dark color: Mafic rocks are typically dark green to black due to the presence of minerals like pyroxene and olivine, which are rich in iron and magnesium.
* Low silica content: Mafic rocks have a silica content of 45-55%, which is lower than felsic rocks (65-75% silica).
Examples of mafic rocks include:
* Basalt: A common volcanic rock found in oceanic crust and lava flows.
* Gabbro: A coarse-grained, intrusive equivalent of basalt.
* Peridotite: A very dense rock found in the upper mantle, with a low silica content and high iron and magnesium content.
It's important to note that the exact composition and appearance can vary, so identifying a rock based on its color and silica content alone might not always be accurate. You may need to perform additional tests to determine the exact type of rock.
