Chalcedony
What is Chalcedony?
Chalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in their crystal structure. Chalcedony has a waxy luster and can be translucent or semi-transparent. It occurs in a wide range of colors, often banded or patterned.
Optical Properties
- Refractive Index
- 1.530-1.540
- Birefringence
- 0.004
- Pleochroism
- Weak to absent
- Optical Character
- uniaxial (+)
- Dispersion
- 0.013
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Chalcedony before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Where to Find Chalcedony
RockHoundR, the free-to-download rockhounding map from the Ruby Glint team, shows where collectors find chalcedony in the US, with land-access notes for BLM land and national forests. Collecting is banned in national parks.
See where to find chalcedonyAlways check the local rules and get the landowner's permission before you collect.
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Quick Facts
Physical Properties
- Color
- White, gray, blue, brown, yellow, pink, red, and green
- Hardness (Mohs)
- 6.5 to 7
- Rock tumbling
- Tumbles well
- Density
- 2.58 to 2.64 g/cm³
- Streak
- White
Chemical Properties
- Chemical Formula
- SiO2
- Elements
- Silicon, Oxygen
Also Known As
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Chalcedony FAQs
How do I identify Chalcedony?
Chalcedony can be identified by its hardness of 6.5 to 7 on the Mohs scale, White color. Look for these key characteristics when examining specimens.
What color is Chalcedony?
Chalcedony typically appears in White, gray, blue, brown, yellow, pink, red, and green. Color can vary depending on impurities and formation conditions.
How hard is Chalcedony?
Chalcedony has a hardness of 6.5 to 7 on the Mohs scale. This gives it moderate hardness.