Chalcedony: This is a term including microcristallines and cryptocrystalline varieties of quartz, which come from the Greek name of the famous city of Carthage “Karkêdon”. Extracted in Egypt and Syria, it has been used since ancient times for intaglios and cameos, an active trade with Carthage being established.
Its base color varies from blue to milky gray through pale mauve, it can be porous, cloudy translucent, blue fluorescent.
The Sardonyx, light brown, reddish brown to dark brown, but even, unlike the “sardonyx” which is zoned.
The Jasper, some integrating it within a particular family. If its name comes from a Greek word meaning speckled stone, in ancient times it meant something very different. Of variable and opaque colors, monochrome jaspers are exceptional, because rather colorful, striped, speckled, flamed, zebra. The Jasper hématoide is also called iron eye.
The Heliotrope, its name comes from what was formerly attributed to it : the possibility to change the color of sunlight when it was immersed in water (“Helios” for sun and “Trepo” for “I turn” in Greek). The ring of Gyges, who, according to Greek mythology, rendered invisible, wore a heliotrope. Its other name “bloodstone” is false because it is not a Jasper, and its English translation (“bloodstone”) has nothing to do with the German word “Blutstein” (blood stone ) which designates the hematite. It is Dark green with red dots, green due to inclusions of chlorite, and red due to iron oxide. In the Middle Ages it was used to represent the crucifixion with blood drops.
The Carnelian is translucent, its name comes from its orange color similar to that of a cornel (dogwood fruit). It was used in antiquity for intaglios and cameos.
The Chrysoprase, his name evokes the golden glow and the color of the leek-green variety of quartz whose fibers have a radial microscopic texture. Its color is due to the presence of inclusions of nickel but may deteriorate after a long exposure to sunlight. This is the most valuable chalcedony.
The mtorolite is a green Cr-chalcedony from Zimbabwe.