Crystal & mineral guide
Chalcedony
SiO₂ (microcrystalline quartz)
Parent microcrystalline quartz of agate, carnelian, onyx, and jasper varieties.
Identify Chalcedony with RockScan Get on the App StoreAbout Chalcedony
Chalcedony is the trade name for translucent unbanded microcrystalline quartz, often blue-gray or lavender. It is the structural parent of agate, carnelian, chrysoprase, and related gems. Smooth waxy polish and toughness make it ideal for cabochons and cameos.
Chalcedony belongs in a crystal identifier workflow because photo cues — color zoning, crystal habit, and surface luster — combine with measurable traits like Mohs 6.5–7 and specific gravity 2.58–2.64. Use RockScan’s camera to get a first-pass ID, then confirm with the checklist below.
Chalcedony properties
| Mohs hardness | 6.5–7 |
|---|---|
| Crystal system | Trigonal (microcrystalline) |
| Luster | Waxy to vitreous |
| Color | Blue-gray, white, lavender, brown |
| Composition | Cryptocrystalline quartz (fibrous microstructure) |
| Formation | Low-temperature silica precipitation from solutions |
| Occurrence | Worldwide; Namibia, Turkey, India, Brazil |
| Specific gravity | 2.58–2.64 |
| Cleavage | None |
How to identify Chalcedony
- Waxy translucent look without visible crystals
- Hardness 7; no cleavage
- RI near quartz (~1.53–1.54)
Collector notes
- Name from the ancient town of Chalcedon (near Istanbul)
- Blue chalcedony from Namibia is a modern jewelry favorite
Value context: Even translucent blue-lavender material brings the strongest jewelry demand.
Chalcedony FAQ
How do you identify Chalcedony?
Chalcedony (SiO₂ (microcrystalline quartz)) is typically recognized by blue-gray, white, lavender, brown color, waxy to vitreous luster, Mohs hardness 6.5–7, and trigonal (microcrystalline) crystal system. RockScan can suggest Chalcedony from a photo and surface these checks on the result card.
What is Chalcedony made of?
Chalcedony composition: Cryptocrystalline quartz (fibrous microstructure). It forms via low-temperature silica precipitation from solutions and is found in Worldwide; Namibia, Turkey, India, Brazil.
Is Chalcedony valuable?
Even translucent blue-lavender material brings the strongest jewelry demand.
