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Gemstone profile and identification guide

Sardonyx

Sardonyx is a banded chalcedony combining sard-colored and onyx-style layers.

7 Mohs Brown, White Silicate (Banded Chalcedony Agate Variety)
Sardonyx

Overview

Sardonyx is a banded chalcedony combining sard-colored and onyx-style layers.

Did you know? Sardonyx was a favored material for Roman cameos and seals.

Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.

Identification

Name: Sardonyx

Scientific classification: Silicate (Banded Chalcedony Agate Variety)

Hardness: 7 Mohs

Transparency: translucent

Lustre: waxy

Crystal system: Trigonal (microcrystalline aggregate)

Primary colour: Brown

Secondary colour: White

Colour family: Browns

Layered sard and white/black bands identify sardonyx category.

Verification Status

Status: verified-core-fields

Reference priority: GIA, Gem-A, Mindat, International Gem Society

Core identity, locality, and physical-property fields reviewed against standard gemological references.

Trade-name and treatment-sensitive entries include explicit disclosure notes where applicable.

Physical Properties

Hardness category: hard

Hardness value: 7 Mohs

Chemical composition: Silicon dioxide (SiO2)

Crystal system: Trigonal (microcrystalline aggregate)

Common locations: India, Brazil, Uruguay, Germany

Learn more: Gem-A gemstone education resources.

Colour Variations

Banded sard (brown-red) and onyx-like white/black chalcedony layers.

Optical effects: Banding

Detailed Gemology

Mineral species: Quartz (banded chalcedony sardonyx variety)

Mineral group: Quartz group

Chemical formula: Silicon dioxide (SiO2)

Mohs hardness: 7

Crystal system: Trigonal (microcrystalline aggregate)

Lustre: waxy

Transparency: translucent

Streak: White

Cleavage: None

Fracture: Conchoidal

Specific gravity: 2.58-2.64

Refractive index: 1.53-1.54

Optical phenomena: Banding

Colour range: Brown-red with white/black layering

Common inclusions: Band boundaries, occasional druzy pockets

Geological environment: Silica-rich volcanic cavity systems

Principal mining regions: India, Brazil, Uruguay, Germany

Important commercial sources: Sardonyx is sourced from agate-bearing localities worldwide

Historical significance: Important historical engraving and seal stone.

Common treatments: Dyeing of chalcedony bands can occur.

Synthetic or imitation forms: Dyed agate and layered glass imitations exist.

Common look-alikes: Onyx, dyed agate, banded chert

Jewellery uses: Used in cameos, intaglios, beads, and cabochons.

Care recommendations: Durable for jewelry and cameos; standard quartz care applies.

Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Sardonyx.

Formation

Forms by rhythmic silica deposition in cavities producing layered band structures.

Origin

Sardonyx is sourced from agate-bearing localities worldwide

Uses

Best for: Used in cameos, intaglios, beads, and cabochons.

Ideal uses: Layered carving work and classic signet styles.

Sardonyx FAQ

How can I identify Sardonyx?

Compare hardness (7 Mohs), crystal system (Trigonal (microcrystalline aggregate)), colour profile, and lustre (waxy) with your sample. Then cross-check related gemstones listed above.

What colour range does Sardonyx appear in?

Banded sard (brown-red) and onyx-like white/black chalcedony layers.

Where is Sardonyx commonly used?

Layered carving work and classic signet styles.. For maintenance, follow the care guidance in this profile.