Extrusive = fine grained (many small grains) – individual crystals cannot be identified with the naked eye and this general texture is termed Aphanitic.;
Intrusive = coarse grained (few large grains > 1 mm) – all crystals are large enough to be seen without a hand lens and this general texture is termed Phaneritic.
If cooling is extremely rapid, crystals do not have a chance to form and the rock is Glassy.

If cooling is extremely slow and the water content of the magma is elevated, extremely large crystals (> 3 cm) develop and such rocks are called Pegmatites and the texture is Pegmatitic.

An igneous rock with two different sizes is termed Porphyritic: larger crystals = Phenocrysts; smaller crystals = Groundmass.

Gas bubbles in lava don’t pop or escape.  The voids left are termed Vesicles and the texture is termed Vesicular.
If the vesicles in some extrusive rocks are filled by secondary minerals (calcite, silica, etc), the filled vesicles are called Amydules and the texture is termed Amygdaloidal.

Pyroclastic Texture = fragmental texture formed by explosive eruptions. As the material falls to the ground, deposits containing shattered volcanic glass, rock, and mineral fragments (collectively termed Pyroclasts) form and are called Tuffs.

Mafic magmas can eject pieces of magma that become streamlinedand cool as they move through  air, falling as Volcanic Bombs.

Mafic Rocks: contain a lot of ferromagnesian (Fe-Mg rich) minerals = dark color.
Felsic Rocks: contain a lot of feldspars and quartz = light minerals.

Mafic rocks crystallize from hotter magmas than felsic rocks (see Bowen’s Reaction Series).

See Table 3.1 for Recognizing Minerals in Igneous Rocks in conjunction with these words.

Classification of Igneous Rocks can be conducted through Mineralogy or Bulk Composition (i.e., Silica content).

Igneous Rocks and Plate Tectonics

Granite
Diorite
Gabbro
Rhyolite
Pumice
Obsidian
Scoria
Vesicular Basalt
Andesite
Porphyritic Basalt
Dunite
Basaltic Volcanic Bomb
Amygdaloidal Basalt
Pegamatite