Cornelian (Red Agate)

Group: Chalcedony -> Quartz Mineral class: Oxides Colour pale red, orange-red, red-brown Colouring substance: iron oxide Pleochroism: absent Mohs’ hardness: 7 Density: 2.6 Cleavage: absent Fracture: irregular, concave Crystal system: trigonal Transparency: semitransparent to opaque Lustre: wax lustre, oily lustre Fluorescence: bluish white. In Indian varieties, yellow-green

For the ancient Egyptians, this gemstone represented the red symbol of life. In this fashion it was linked to diverse religious practices and had the task of accompanying the deceased into the underworld. Thus it decorated the pectoral belt of Tutenkamon. Because of its ideal suitability for engraving, it was widespread in ancient civilizations. Many examples have been found from the Etruscan, Ancient Greek and Roman civilisations. It was also supposed to have curative powers in case of loss of blood as well as being considered a powerful protection against witchcraft.

The Cornelian is a very well known variety of chalcedony, a microscopically fine quartz aggregate. It is an opaque stone, and if cut very finely can be semitransparent. The most sought-after colour is red-orange, which comes from iron oxide. The paler varieties (pale red) come from iron hydroxide. Via light heating, more intense tones can be achieved. A similar result can be accomplished by immersing the stone in iron sulphate. Because the Cornelian is an opaque mineral, inclusions cannot be seen, excepting some halos in the form of clouds (liquid drops) and fractures of the stone. Its Mohs’ hardness is 7 (as in all minerals from the quartz group), which makes it an excellent gemstone for inclusion in engraving works, cabochon cuts and beads for necklaces.

Cornelian can be found in nature in grape bundle forms, stalactites and groupings, with a typical radial structure. The most important deposits were discovered by the ancient Romans and are in Arabia, India and Persia. Today Cornelian is also found in Brazil and Uruguay.

Cornelian is a fine gemstone for cabochon cuts, engravings and beads for necklaces.

Japes, some corals.