Igneous Rocks

Ignimbrite is an expansion of hardened tuff. Ignimbrites are igneous rocks made up by crystal and rock fragments in a glass-shard groundmass, albeit the original texture of the groundmass is probably obliterated due to high degrees of welding. The term ignimbrite isn't always encouraged by means of the IUGS Subcommission on the Systematics of Igneous Rocks.

Granodiorite  is a phaneritic-textured intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. According to the QAPF diagram, granodiorite has a greater than 20% quartz by volume, and between 65% to 90% of the feldspar is plagioclase. A greater amount of plagioclase would designate the rock as tonalite.

This volcanic rock is named after the Andes Mountains. Intermediate in silica content, it is usually gray in color and may be fine-grained or porphyritic. Andesite is the volcanic equivalent of diorite. It consists of the plagioclase feldspar minerals andesine and oligoclase, together with one or more dark

Medium or coarse grained rocks, gabbros Dark green pyroxene in principle (augite and smaller orthopyroxene amounts plus white or green colored plagioclase and black, millimeter sized grains of magnetite and / or ilmenite.

Basalt is the most common rock on Earth’s surface. Specimens are black in color and weather to dark green or brown. Basalt is rich in iron and magnesium and is mainly composed of olivine, pyroxene, and plagioclase. Most specimens are compact, fine-grained, and glassy. They can also be porphyritic, with phenocrysts of olivine, augite, or plagioclase. Holes left by gas bubbles can give basalt a coarsely porous texture.