The first step involves determining the texture of your unknown rock sample. There are several basic textural types: phaneritic, aphanitic, porphyritic, glassy, vesicular and fragmental. Examples of each are shown below.  Let's examine your rock. CLICK on the appropriate texture to move to the next identification step.

Phaneritic (coarse-grained) texture. All of the mineral grains should be visible with the unaided eye.
Aphanitic (fine-grained) texture. Most or all of the mineral grains cannot be seen with the unaided eye. There may be some scattered larger mineral grains present.		Some samples might have a slight vesicular texture.  A rock can be both Aphanitic and Vesicular
Porphyritic (mixed-grained) An aphanitic rock that also has multiple scattered larger mineral grains present.
Glassy texture. No mineral grains are present, the rock is comprised entirely of glass.
Vesicular texture. No mineral grains are present, the rock is light-weight and contains numerous holes or cavities.
Fragmental (Pyroclastic) texture. Rock fragments and glass shards embedded in a fine-grained (ash) matrix.