Mexican Fire Agate a variety of chalcedony (SiO2), is a semi-precious natural gemstone found only in certain areas of northern Mexico and the southwestern United States.There is no actual object inside the stone, this special effect arises from light
Thierry Cohen made these by combining the daylight pics of the cities and the pristine skyline of the desert at the same latitude, direction, and angle. He wants to show what city dwellers would see without all the light pollution