Igneous rocks formed from cooling magma deep beneath the Earth's surface typically have a phaneritic texture. This means that the individual mineral crystals are large enough to be seen with the naked eye.

Here's why:

* Slow Cooling: Magma deep underground cools very slowly. This gives the mineral crystals ample time to grow and form large, well-defined crystals.

* Intrusive Formation: These rocks are formed when magma intrudes into existing rock layers, creating formations like batholiths, dikes, and sills. This slow cooling process further promotes the growth of large crystals.

Examples of phaneritic igneous rocks:

* Granite: Composed of quartz, feldspar, and mica.

* Gabbro: Composed of pyroxene, plagioclase feldspar, and olivine.

* Diorite: Composed of plagioclase feldspar and hornblende.

It's important to note that some igneous rocks formed deep underground can have a porphyritic texture. This means that they contain larger crystals (phenocrysts) embedded in a finer-grained matrix (groundmass). This occurs when the magma cools in stages, allowing some crystals to grow larger before the rest of the magma solidifies.