atoll structure

Ring-shaped crystal in thin section surrounding a mineral aggregate similar to the matrix. Atoll structures of garnet are common in some mica-schists and probably form as corona structures, followed by breakdown of the crystal around which they originally formed

Related terms:

• atoll texture
• Atoll
• core-and-mantle structure
• Mineral Structure
• mortar structure
• quarter structure
• quartz ribbon
• drowned atoll
• window structure
• ring structure