Moqui marbles are typically small, brownish-black balls composed of iron oxide and sandstone that formed underground when iron minerals precipitated from flowing groundwater. Some of their properties include: grounding, energizing and cleansing. excellent aid for spiritual and intuitive growth. studies show that the Moqui balls were formed at ages that range from 300, 000 years ago to 5 million years ago which is "a sharp contrast to the 190-million-year-age of the Navajo Sandstone."