pegmatite
/ˈpɛɡmətaɪt/
noun
- A very coarse-grained igneous rock, often containing large crystals of minerals like quartz, feldspar, and mica.
- The museum displayed a beautiful piece of pegmatite with crystals as big as your hand.
- Miners sometimes find valuable gemstones like tourmaline in pegmatite deposits.
- Geologists study pegmatite to understand how large crystals form deep underground.