The extrusive rock with a composition similar to granite but smaller crystals is called rhyolite.

Here's why:

* Composition: Both granite and rhyolite are felsic rocks, meaning they are rich in silica and have high amounts of quartz and feldspar.

* Crystal Size: Granite is an intrusive rock, meaning it cools slowly underground, allowing for larger crystals to form. Rhyolite, on the other hand, is an extrusive rock, formed when lava cools quickly on the Earth's surface. This rapid cooling results in smaller crystals.

So, while granite and rhyolite share a similar chemical makeup, their crystal size differences reflect their different formation environments.