I wonder if the rays are original or a later addition.
It served as the coronation stone for the High Kings of Ireland. It is also known as the Coronation Stone of Tara. In legend, all of the kings of Ireland were crowned on the stone up to Muirchertach mac Ercae c. AD 500.
Tens of centuries ago, amid Ireland’s iconic green, rolling landscape, the kings of Ireland were anointed on a hill of tremendous importance—a place where spirituality met with royalty, and mythical traditions began. The Hill of Tara, one of the most revered spiritual sites in Ireland, is a place where druids held festivals, priestesses were trained and shaman’s rites were performed. Dating back to about 4000 B.C., Tara’s importance to the Irish has withstood the test of time, and has remained a place of political and spiritual significance to pre-Christian and Christian Irish society alike.