Carnelian, sometimes spelled cornelian, is a red or reddish-brown variant of chalcedony. Similar to carnelian is sard, which is generally harder and darker.
The words carnelian and sard are often used interchangeably, but they can also be used to describe distinct subvarieties. The purported differences are as follows:
Carnelian
Sard
Colour
Lighter, with shades ranging from orange to reddish-brown.
Darker, with shades ranging from a deep reddish-brown to almost black.
Hardness
Softer
Harder and tougher.
Fracture
Uneven, splintery and conchoidal
Like carnelian, but duller and more hackley.
It should be noted that all of these properties vary across a continuum, and so the boundary between carnelian and sard is inevitably blurred.
Carnelian was used widely during Roman times 2,000 years before the present era to make signet or seal rings for imprinting a seal with wax on correspondence or other important documents. Hot wax does not stick to Carnelian. [2]
The word carnelian is derived from the Latin word meaning horn, in reference to the flesh color sometimes exhibited.
Folklore
Carnelian is the zodiac birthstone of Virgo according to some texts. It is also one of the gemstones (along with peridot, diamond and sapphire) that has been associated with the month August.
