mineral
Chalcedony (Yellow/Amber variety)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Honey-yellow, translucent to opaque; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (trigonal/monoclinic); Cleavage: None; Fracture: Conchoidal.
- Hardness
- 6
- Color
- Honey-yellow, translucent to opaque
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Honey-yellow, translucent to opaque; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (trigonal/monoclinic); Cleavage: None; Fracture: Conchoidal.
Formation & geological history
Formed through the deposition of silica from aqueous solutions, typically in volcanic cavities (vesicles) or sedimentary environments. It develops as a microcrystalline mass over thousands of years.
Uses & applications
Commonly used for lapidary work, jewelry (cabs or beads), tumbled stones for healing practices, and as a collector's specimen.
Geological facts
Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen under a normal microscope. The yellow color is often attributed to trace inclusions of iron hydroxides like goethite.
Field identification & locations
Identify in the field by its waxy luster, lack of visible crystals, and its ability to scratch glass. Found worldwide in riverbeds, deserts, and volcanic regions. Common locations include Brazil, India, and the USA (southwest).
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