How can you tell if the rock is igneous?

Determine the color (indicates mineral composition)

Determine the texture (indicates cooling history)

Phaneritic: large grains.

Aphanitic: small grains (too small to identify with the naked eye)

Porphyritic: fine grains mixed with larger grains.

Vesicular: holes.

Glassy: glass-like.

Explanation:

Things like this determine if its igneous or not.