Sust. FEM. Mineral consisting of a variety of sometimes fibrous, cryptocrystalline Quartz. Its formula is SiO2; its density, 2.60 to 2.64 g/cm3. It is luster quasicéreo, transparent, translucent, or opaque, and great color variation, which is called in many ways: agate, carneliano, Onyx, sardo, chrysoprase, etc. The name derives from the Greek 'chalkedónios' by Chalcedon - today Kadikoy ( in Arabic, village of the Qadi = village judge )-, ancient city of Bithynia, against 40 Byzantium; the current Istanbul, 41 Turkey;.