Metamorphic Rock

Gneiss is a Plutonic metamorphic rock which is formed under high pressure and temperature condition at Katazone or Lower Zone.

The two metamorphic rocks that typically exhibit the largest crystals are gneiss and schist. Gneiss often features large, visible grains of quartz and feldspar, while schist is characterized by its shiny, platy minerals like mica that can form significant crystal sizes. These large crystals usually develop in environments with high temperatures and pressures, allowing minerals to grow and recrystallize.

Metamorphic rocks are formed from existing rocks that undergo changes due to heat, pressure, and chemically active fluids. They often exhibit foliation, which is the alignment of mineral grains, or may appear non-foliated, depending on their formation conditions. Common properties include increased density and hardness, as well as the presence of new minerals that form under metamorphic conditions. Examples include schist, gneiss, and marble.

Metamorphic rocks formed by contact metamorphism are dense and resistant primarily due to the intense heat and pressure they experience from nearby molten magma or lava. This process causes the minerals within the rock to recrystallize, often resulting in a more compact and tightly interlocked structure. Additionally, the high temperatures can lead to the formation of minerals that are inherently more durable, contributing to the overall density and resistance of the rock.

No, a metamorphic rock cannot be created through melting. Metamorphic rocks form from existing rocks—either igneous, sedimentary, or other metamorphic rocks—through a process called metamorphism, which involves heat, pressure, and chemically active fluids, but not melting. If a rock melts, it transforms into magma, which upon cooling can form igneous rock instead. Therefore, while heat is involved in both processes, melting is a key distinction that separates the formation of igneous rocks from metamorphic ones.