Cryptocrystalline variety of quartz with a waxy luster. Includes many sub-varieties such as agate, carnelian, and jasper. Color: Variable - white, gray, blue, brown. Luster: Waxy to vitreous. Streak: White. Cleavage: None. Hardness: 6.5-7. Transparency: Translucent to opaque. Crystal system: Hexagonal Trigonal. Chemical formula: SiO₂. Specific gravity: 2.59-2.61. Formation: Precipitates from silica-rich solutions at low temperatures in cavities and fractures in rocks. Common geological settings: Worldwide; common in volcanic and sedimentary rocks, especially in agate geodes. Common look-alikes and related entries: Opal, Chert, Jasper.
These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.
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GeoMiner
Last updated
2026-03-30T14:36:42.378972+00:00
Review status
Published; not independently peer-reviewed
IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.
Cryptocrystalline variety of quartz with a waxy luster. Includes many sub-varieties such as agate, carnelian, and jasper.
How can you identify Chalcedony?
Compare several properties rather than relying on colour alone. This entry records colour: Variable - white, gray, blue, brown; lustre: Waxy to vitreous; streak: White; Mohs hardness: 6.5-7; cleavage: None; crystal system: Hexagonal Trigonal; transparency: Translucent to opaque. Confirm an important identification with additional field tests or qualified laboratory work.
How does Chalcedony form?
Precipitates from silica-rich solutions at low temperatures in cavities and fractures in rocks.
Where is Chalcedony commonly found?
Worldwide; common in volcanic and sedimentary rocks, especially in agate geodes.
What is Chalcedony commonly confused with?
Chalcedony may be confused with Opal, Chert, Jasper. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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