The formation of atoll garnet in the Ardara aureole, NW Ireland, is discussedusing the textural, chemical and Electron Backscatter Diffraction (EBSD) data.Textural evidence suggests the possibility of incipient of garnet replacement fromthe core. In addition, the presence of staurolite and andalusite in the core of smallatoll garnets as well as the occurrence of sillimanite in the core of large atollgarnet reveal the prograde nature of atoll formation. The microprobe analyses andEBSD data also indicate that atoll garnets in the Ardara aureole developed by pre-existing idioblastic garnets being replaced by mainly biotite to produce atoll form

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