Translucent, semiprecious variety of the silica mineral chalcedony that owes its red to reddish brown colour to the incorporation of small amounts of iron oxide. A closely related variety of chalcedony, sard, differs only in the shade of red. Carnelian was highly valued and used in rings and signets by the Greeks and Romans, some of whose intaglios have retained their high polish better than those made from harder stones. Carnelian is mined principally in India, Brazil, and Australia. Its physical properties are those of quartz.
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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:
|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.
The word carnelian is derived from the Latin word caro, carnis meaning flesh, in reference to the flesh color sometimes exhibited.