The nameless and formless God takes many forms for the sake of devotees. The forms differ according to the nature of the worshipper.
From the book " Vasantha Sai Brindavan Satsang
Lord of the Rings
One day at satsang just before meditation, Nicola from the U.K. gave Amma a new ring she had purchased only that morning with the help of a friend. Her friend was also there for meditation.Vasantha: She asked me to put it on my finger (aw a way of blessing it). I did this. Afterwards I gave it back to her without thinking about it. I forgot I was wearing it.
Eddy happened to look at the white clear jewel and saw to his surprise Swami's image there. All who were there could see Swami standing deep inside the white stone of the ring. Nicola attended the satsangs regularly and sang bhajans beautifully.