Aphanitic texture consists of small crystals that cannot be seen by the eye with or hand lens. Yes, I know the cartoon above is rather crude, but it gets the point across. Aphanitic rocks are characterized by textures in which the mineral grains are not visible to the eye so they generally look rather like a blank slate. Of course, this represents an ideal world. This often causes the lay person to assume a phaneritic texture, but with a little practice you will find you can quickly distinguish between aphanitic and phaneritic textures.
Porphyritic texture is really a subtype, but usage of the term often confuses the beginner.
Both aphanitic and phaneritic rocks can be porphyritic, but the former are far more common. Most often the porphritic term is utilized as a modifier. Glassy Texture Glassy textured igneous rocks are non-crystalline meaning the rock contains no mineral grains. Glass results from cooling that is so fast that minerals do not have a chance to crystallize. This may happen when magma or lava comes into quick contact with much cooler materials near the Earth's surface.