amygdule
/əˈmɪɡdul/
noun
- A small, almond-shaped cavity in volcanic rock that is often filled with minerals.
- Each amygdule in the basalt was lined with tiny, sparkling calcite crystals.
- The hiker found a beautiful amygdule filled with quartz crystals.
- Geologists study amygdules to learn about the minerals present in ancient lava flows.