'Diamond Ring' is a phenomenon observed

1. A total solar eclipse occurs when the Moon completely blocks the Sun's disk as viewed from Earth. 2. The 'Diamond Ring' effect is a visual phenomenon observed just before totality begins and just after totality ends. 3. As the Moon moves to cover the last sliver of the Sun's photosphere, the rugged lunar limb (edge with mountains and valleys) allows beads of sunlight to shine through in some places (Baily's beads). 4. When only one bead of sunlight remains, shining brightly against the faint corona (Sun's outer atmosphere) which becomes visible just before totality, it creates a fleeting resemblance to a diamond ring. 5. A similar effect occurs in reverse order just as totality ends and the first sliver of the Sun reappears. 6. Therefore, it is observed both at the start and the end of a total solar eclipse.