The intrusive igneous rock that contains unusually large mineral grains is called:

Correct option is C

Pegmatite is an intrusive igneous rock characterized by its extremely large crystals. It forms during the final stages of magma crystallization when minerals can grow to very large sizes due to the high concentration of water and other volatiles in the magma. These volatile elements lower the viscosity of the magma, enabling rapid growth of large mineral grains.
· Key Features of Pegmatite:
· Contains crystals often larger than 1 cm and can even reach sizes of several meters.
· Typically composed of quartz, feldspar, and mica, but may also contain rare minerals such as tourmaline, beryl, and spodumene.
Pegmatites often form as veins or pockets within larger igneous intrusions and are important sources of rare earth elements and gemstones.
Key Points: 1. Formation:
· Pegmatites form from the residual magma that is rich in water and other volatiles.
2. Composition:
· Mainly quartz, feldspar, and mica, but may also include rare minerals.
3. Crystal Size:
· Crystals are exceptionally large compared to other igneous rocks.
4. Economic Importance:
· Pegmatites are significant sources of industrial minerals and gemstones like tourmaline and beryl.
5. Rare Elements:
· Often enriched with rare elements like lithium, tantalum, and niobium.