Short answers, pulled from the story.
Igneous rock is the solidified remains of magma or lava, the molten material that rises from deep within the Earth. These rocks form the foundation of the planet and make up 90 to 95 percent of the top 16 kilometers of the Earth's crust by volume.
When magma cools slowly within the Earth's crust, it forms intrusive igneous rocks like granite with large mineral grains visible to the naked eye. In contrast, when magma reaches the surface as lava and cools rapidly, it results in extrusive igneous rocks that are fine-grained or even glassy.
Silica, or silicon dioxide, is the single most important component that determines whether a rock is classified as felsic, intermediate, mafic, or ultramafic. Felsic rocks are rich in silica and quartz while mafic rocks are low in silica but high in iron and magnesium.
Magma is born from an increase in temperature, a decrease in pressure, or a change in composition. Decompression melting occurs when mantle rock rises and expands, while the addition of water lowers the melting point of rocks to drive formation in subduction zones.
The word basalt dates back to 1546, when Georgius Agricola described it in his work De Natura Fossilium. The term granite has been in use since the 1640s, derived from the French granit or Italian granito.