Carnelian, being a Chalcedony gemstone, can sometimes have its classification borderline with other Chalcedony gemstones. Sard, which is the brownish to brownish-red translucent form of Chalcedony, can sometimes be a color that can fall under either category. The name Sard can also be used interchangeably with Carnelian, though it is accepted that Carnelian on the redder spectrum and Sard on the browner spectrum. Sard has more historical significance over practical usage, as it is not commonly used as gemstone today.
Carnelian differs from Jasper in that Jasper will always be opaque, whereas Carnelian is translucent. Carnelian may be nearly opaque but will still let light through when viewed from the edges. Jasper usually also exhibits multicolored patterns and splotches which are lacking in Carnelian. Though Carnelian is often a solid color, it may contain lighter and darker zones within a single stone, or cloudy areas.
Carnelian is a minor jewelry gemstone. It is cut and polished into cabochons, and used as beads for necklaces and bracelets. It is also carved into cameos which can be worn as pendants. Carnelian is occasionally used as an ornamental stone and carved into animal carvings or ornamental objects.
Carnelian Agate – Banded form of Carnelian. May be correctly classified both as Carnelian and Agate.
Carnelian Onyx – Agate/Carnelian composed of red and white banding lines. Synonym of Sardonyx.Most Carnelian is naturally colored, though some lighter-toned stones may be heat treated to enhance color. Some Carnelian on the market is dyed white Chalcedony or lightly colored Agate.Sources of Carnelian include India, Brazil, Uruguay, and the Unites States (New Jersey and Oregon).Fire Opal is usually a brighter color and more transparent than Carnelian, and is always softer. Amber may resemble Carnelian, but it is much softer. Cat’s Eye describes a gemstone polished into a cabochon that displays a narrow band of concentrated light going accross the width of the stone. This effect, known as chatoyancy, or cat’s eye effect, is caused by inclusions of fine, slender parallel mineral fibers in the gemstone that reflect light in a single band. Of all the gemstones that exhibit cat’s eye, Chrysoberyl Cat’s Eye is the best known. Chrysoberyl has the strongest and most distinct cat’s eye effect of all gemstones. Though several different gemstones types exhibit a cat’s eye effect, only Chrysoberyl’s cat’s eye enjoys the privilege of having the name “Cat’s Eye” without any prefix. Whenever the term “Cat’s Eye” is used, it refers to Chrysoberyl cat’s eye by default, unless otherwise specified.
Carnelian TREATMENTS AND ENHANCEMENTS
Chemical Formula BeAl2O4
Color Blue, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Multicolored
Crystal System Orthorhombic
Refractive Index 1.744 – 1.755
SG 3.5 – 3.8
Double Refraction .009
Cleavage 1,1 ; 3,2
Mineral Class Chrysoberyl