This gorgeous circular 3.5" black slate altar tile features a beautiful engraved Stropholos of Hecate.
 
The Stropholos of Hecate, also known as Hecate's wheel is an ancient Greek symbol used to represent the Moon Goddess Hecate.  It is said to be the depiction of a labyrinthine serpent around a central spiral. The labyrinthine snake is representative of rebirth + renewal and relates to the three faces of Hecate.