Sardonyx
What is Sardonyx?
Sardonyx is a variety of chalcedony, a cryptocrystalline form of silica. It is characterized by its parallel bands of sard (brownish-red to orange) and onyx (black or white). The name is derived from the combination of sard, referring to the reddish-brown color, and onyx, referring to the banded appearance. Sardonyx is prized for its durability, luster, and the striking contrast of its bands, making it a popular choice for jewelry and ornamental objects.
Optical Properties
- Refractive Index
- 1.530-1.540
- Birefringence
- None
- Pleochroism
- None
- Optical Character
- Isotropic
- Dispersion
- Low
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Sardonyx 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.
Sardonyx Localities Map
See where Sardonyx is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Quick Facts
Physical Properties
- Color
- Brownish-red, orange, white, black
- Hardness (Mohs)
- 6.5 - 7
- Density
- 2.60 - 2.65 g/cm³
- Streak
- White
- Luster
- Vitreous to waxy
Chemical Properties
- Chemical Formula
- (Si,Al)O2
- Elements
- Silicon, oxygen, aluminum, iron
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Sardonyx FAQs
How do I identify Sardonyx?
Sardonyx can be identified by its hardness of 6.5 - 7 on the Mohs scale, Brownish-red color, Vitreous to waxy luster. Look for these key characteristics when examining specimens.
What color is Sardonyx?
Sardonyx typically appears in Brownish-red, orange, white, black. Color can vary depending on impurities and formation conditions.
How hard is Sardonyx?
Sardonyx has a hardness of 6.5 - 7 on the Mohs scale. This gives it moderate hardness.