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•  comprised of large crystals that are clearly visible to the eye with or without a hand lens or binocular microscope.
•  large crystals are generally > 1/2 mm to several centimeters in size
•  forms by slow cooling of magma deep underground in the plutonic environment.
• in order to be truly phaneritic all of the mineral grains must be visible. 
• Forms by slow cooling of viscous magma, and or good nucleation.

 small crystals that cannot be seen by the eye with or hand lens.

 crystals are generally < 1/2 mm in size.

This texture results from rapid cooling in volcanic or hypabyssal (shallow subsurface) environments.

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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.

Formed from rapid cooling, fluid lava, and/or good nucleation 

 composed of at least two minerals having a conspicuous (large) difference in grain size.

The larger grains are termed phenocrysts and the finer grains either matrix or groundmass (see the drawing below and image to the left).

Porphyritic rocks are thought to have undergone two stages of cooling; one at depth where the larger phenocrysts formed and a second at or near the surface where the matrix grains crystallized.

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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.

For instance, an andesite with visible phenocrysts of plagioclase feldspar would be termed an andesite porphyry or porphyritic andesite (see photo above).

Forms from slow, then rapid cooling and/or change in magma viscosity or comp. 

• 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.
• Pure volcanic glass is known as obsidian (see photo).
• Forms from rapid cooling and or poor nucleation 

• This term refers to vesicles (holes, pores, or cavities) within the igneous rock.
• Vesicles are the result of gas expansion (bubbles), which often occurs during volcanic eruptions.
• Pumice and scoria are common types of vesicular rocks.