Crystals in intrusive rocks are arranged in a phaneritic texture, which means that the crystals are large enough to be seen with the naked eye. This is due to the slow cooling process of magma deep beneath the Earth's surface.

Here's a breakdown of how this arrangement comes about:

* Slow Cooling: Magma that intrudes into the Earth's crust cools much slower than lava that erupts at the surface. This slow cooling allows the crystals to grow larger.

* Abundant Space: Magma chambers provide ample space for crystals to grow without being hindered by rapid cooling or a lack of space.

* Crystal Growth: As the magma cools, mineral ions start to bond together and form crystals. With time, these crystals grow larger, often interlocking with each other.

Here are some common crystal arrangements in intrusive rocks:

* Equigranular: Crystals are roughly the same size and shape.

* Porphyritic: Large crystals (phenocrysts) are embedded in a matrix of smaller crystals (groundmass).

* Pegmatitic: Very large crystals (often several centimeters or larger) are found in a coarse-grained texture.

Examples of intrusive rocks with phaneritic textures:

* Granite: A common intrusive rock with large, interlocking crystals of quartz, feldspar, and mica.

* Diorite: Another intrusive rock with a phaneritic texture, containing plagioclase feldspar, hornblende, and often biotite mica.

* Gabbro: A dark-colored intrusive rock with large crystals of pyroxene and plagioclase feldspar.

In summary, the slow cooling process and ample space in magma chambers allow crystals in intrusive rocks to grow large and form the characteristic phaneritic texture. This texture is one of the defining features of intrusive rocks.