Carnelian | Gemopedia

Carnelian is a translucent orange to red variety of chalcedony. Uniformly colored cryptocrystalline quartz, its red tints are caused by traces of iron oxide. The name is derived from the Latin world for flesh, carne, due to its orangey red color. Carnelian has been appreciated since antiquity, and is one of the first known materials ever to be used as a gemstone.
Alternate
Names
Cornelian
Colors
Orangy Red To Brownish Red To Brownish Orange

Carnelian Classification

Common Name

Carnelian

Species

Quartz

Variety

Chalcedony

Colors

Orangy Red To Brownish Red To Brownish Orange

Alternate Names

Cornelian

Gemstone Groups

Key Separations

RI, SG, appearance and fracture.

Comments

Color is key to its designation. Lighter and more saturated than sard. Iron is the coloring agent.

Carnelian Optical Properties

Transparency

Semitransparent - Translucent

Refractive Index

1.535-1.539

Birefringence

0.004-0.004

Optic Character

Uniaxial

Optic Sign

Positive

Polariscope Reaction

Aggregate (AGG)

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Pleochroism

None

Dispersion

Strength: none

Comments

Carnelian Chemistry & Crystallography

Chemical Name

silicon dioxide (aka silica)

Chemical Formula

SiO2

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Polycrystalline

Comments

Carnelian Characteristic Physical Properties

Hardness

6.5-7

Streak

Specific Gravity

2.55-2.7 Typical:2.6

Toughness

Excellent

Inclusions

Carnelian sometimes has a cloudy appearance. If stripes are seen through transmitted light then it is dyed agate.

Luster

Vitreous

Stability

Good

Fracture

Conchoidal, Granular

Cleavage

None

Comments

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