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: Carnelian & Sard

Carnelian & Sard used in Jewelry

Source: Occuring worldwide

Carnelian (aka cornelian or sard) is an translucent to opaque orange-red, brownish-red, pure red, or pale yellow variety of chalcedony (quartz) that occurs worldwide. Carnelian is formed by silica-rich water percolating through cavities and fissures in volcanic rock.

Carnelian was used in ornamental objects and jewelry throughout ancient Egypt, Persia, and Sumeria as early as 3000 BC. The name "sard" is derived from one of the places that the stone was found, near the ancient Roman city Sardius (below, right), in the kingdom of Lydia, now in the Manisa province of of modern day Turkey. During Roman times, Carnelian was a popular stone for use in cameos, intaglios, and signet rings.

Bernd Munsteiner cut Carnelian, Michael Zobel setting

Ancient Roman city of Sardius (photo: public domain)

The German village of Idar-Oberstein grew around the mining and cutting of agate and carnelian in the 1400s. Carnelian is a relatively porous material that is easily dyed to alter or enhance the pure red color.

Carnelian belongs to the tectosilicate quartz family of minerals that include chalcedony, agate, onyx, and jasper. Carnelian is typically associated with igneous rock, grown in pegmatites and geodes that formed during the mountain-building process.

Carnelian (Microcrystalline Quartz) Chemistry & Physical Properties

Crystal System	rhombohedral microcrystalline
Crystal Habit	cryptocrystalline
Specific gravity (SG)	2.58 - 2.61
Mohs Hardness Scale	7
Toughness	good
Fracture	conchoidal, uneven, splintery
Cleavage	none
Streak	white
Chemical Composition	SiO₂ (Quartz)

Carnelian (Microcrystalline Quartz) Optical Properties

Optical Properties	singly refractive
Refractive Index	1.530 - 1.550
Birefringence	+0.004
Pleochroism	none
Surface Luster	dull, greasy, silky, waxy
Diaphaneity	translucent, subtranslucent, opaque
Gem Color	brownish-red, orange-red, red

Bibliography and Reference on Carnelian & Sard

1. Judith Crowe, The Jeweler's Directory of Gemstones . DK Publishing.

2. A.C. Akhavan, Twinning in Quartz Crystals www.quartzpage.de

3. GIA, Characteristics of Citrine, Amethyst & Smoky Quartz www.gia.edu

4. Renee Newman, Gemstone Buying Guide . International Jewelry Publications; 2nd edition

5. Antoinette L . Matlins, Antonio C. Bonanno, Gem Identification Made Easy . Gemstone Press

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