Nov 25, 2025 · Rock, in geology, naturally occurring and coherent aggregate of one or more minerals. Such aggregates constitute the basic unit of which the solid Earth is composed and …

Because protolith compositions and the pressure-temperature conditions under which they may be placed vary widely, the diversity of metamorphic rock types is large.

Dec 17, 2025 · Specific varieties discussed below include siliceous rocks (cherts), phosphate rocks (phosphorites), evaporites, iron-rich sedimentary rocks (iron formations and ironstones), …

Oct 18, 2025 · Some common metamorphic rock types are described here. Rocks in which metamorphic minerals are easily seen by eye or hand lens and in which the mineral grains …

Magma rises to Earth's surface, such as through a volcanic eruption, where it cools and hardens into igneous rock. On the surface, weathering and erosion break down the igneous rock into …

Nov 6, 2025 · Specific varieties discussed below include siliceous rocks (cherts), phosphate rocks (phosphorites), evaporites, iron-rich sedimentary rocks (iron formations and ironstones), and …

Oct 31, 2025 · This results in two groups: (1) plutonic intrusive igneous rocks that solidified deep within the crust and (2) volcanic, or extrusive, igneous rocks formed at Earth’s surface.

Dec 9, 2025 · Obsidian is an igneous rock occurring as a natural glass that is formed by the rapid cooling of viscous lava from volcanoes.

Despite the wide variety of igneous and sedimentary rock types that can recrystallize into metamorphic rocks, most metamorphic rocks can be described with reference to only four …

Dec 17, 2025 · Most significantly, they are the single most useful sedimentary rock type for deciphering Earth history. Sandstone mineralogy is the best indicator of sedimentary …