You are given a specimen of rhyolite and a specimen of granite. What method would you use to differentiate them? How can you tell which specimen is more likely volcanic and which is more likely plutonic? Include the terms phaneritic and aphanitic in your answer
I would primarily use texture to differentiate between the two.
Rhyolite - If cooling takes place rapidly as in lava flows (volcanic), the rate at which mineral nuclei form exceeds the rate of growth and an aggregate of many small mineral grains forms. The result is a fine-grained or aphanitic texture, in which individual minerals are too small to be seen without magnification.
Granite - If cooling is slow, the rate of growth exceeds the rate of nuclei formation, and large mineral grains form, thus yielding a coarse-grained or phaneritic texture, in which minerals are clearly visible. Rocks with phaneritic textures are commonly intrusive (plutonic).
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