An igneous rock with both large and small crystals is called a porphyritic rock.

Here's why:

* Porphyritic texture: This texture is characterized by the presence of large crystals (called phenocrysts) embedded in a matrix of smaller crystals (called groundmass).

* Formation: Porphyritic rocks form when magma cools slowly, allowing large crystals to grow. Then, the magma cools more rapidly, resulting in the formation of smaller crystals in the groundmass.

Example: Granite is a common example of a porphyritic igneous rock. It often features large quartz and feldspar crystals embedded in a finer-grained matrix of other minerals.