Sard

Quartz

by Tim Matthews
Published: June 2014
Modified: August 2021
Sard Polished Sard Jewelry

Sard is a translucent chalcedony that is light to dark reddish-brown. It is formed from the deposition of silica at low temperatures from silica-rich waters percolating through cracks and fissures in other rocks. Sard is darker and browner in tone than carnelian.

General Information

Common Name
Sard
Species
Quartz
Transparency
Semitransparent - Semitranslucent
Dispersion
Strength: None
Refractive Index
1.535-1.539
Birefringence
0.004
Optic Character
Uniaxial
Optic Sign
Positive
Polariscope Reaction
Aggregate (AGG)
Fluorescence
SWUV: Inert
LWUV: Inert
Pleochroism
None
Hardness
6.5-7
Streak
White
Specific Gravity
2.550-2.700 Typical:2.600
Toughness
Excellent
Luster
Vitreous, Greasy
Stability
Good
Fracture
Conchoidal, Granular
Cleavage
None
Chemical Name
silicon dioxide (aka silica)
Chemical Formula
SiO2
Crystal System
Trigonal
Chemistry Classification
Silicate

Sard Colors

  • Brown Sard
    Brown

Countries of Origin

Unknown

Care

Normal care