A "kidney" is not necessarily a very elegant name to define this group of crystals in the shape of a rounded mound. In any case, it is in Uruguay that these crystals of Citrine were born. In a pocket of air frozen in the cooling lava, infiltrations of water charged, among others of iron ores, in the form of ultramicroscopic particles of ferric hydroxides, and under the action of heat, they crystallized very well distributed inside the crystal. It took high temperatures (about 550 degrees) to achieve this result. A natural irradiation pushed this citrine to these tones of amber, more orange.