Chalcedony – an astonishing mineral, a cryptocrystalline form of silicon dioxide (quartz), valued for its beauty, diverse colors, and translucent texture with a characteristic waxy luster. It forms from microscopic quartz crystals that are tightly intergrown, often creating botryoidal aggregates, concretions, veins, or filling cavities in rocks.
Chalcedony is the basis for many popular jewelry and ornamental stones, such as agate (a banded variety), carnelian (red/orange), chrysoprase (green), onyx (black and white or contrasting bands), and others.
The color palette of chalcedony is incredibly broad: from milky white, gray, and blue to pink, yellow, orange, rich red, and brown. Sometimes it is almost transparent, but more often translucent or semi-transparent. Its Mohs hardness is 6.5-7, making it durable enough for use in jewelry and for creating carved objects.
The name "chalcedony" is believed to originate from the ancient Greek port city of Chalcedon in Asia Minor, which was a renowned trade center for this stone in antiquity. Ancient civilizations valued it, using it to create seals, amulets, jewelry, and household items.
Today, chalcedony remains a popular choice for jewelers, designers, and collectors due to its natural aesthetic, variety of colors and patterns, excellent polish, and relative accessibility. It is ideal for creating cabochons, beads, pendants, and decorative carvings.
Physical properties
Chemical formula
SiO₂ (silicon dioxide)
Hardness
6.5 - 7 on the Mohs scale
Crystal system
Trigonal (microcrystalline structure)
Transparency
Translucent, semi-transparent, rarely opaque
Luster
Waxy, sometimes dull or vitreous
Color
Diverse: white, gray, blue, pink, yellow, orange, red, brown, green, black; often banded (agate) or patterned
Specific gravity
2.58–2.64 g/cm³
Jewelry with this mineral
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