Black Onyx | Gemopedia

Onyx is a chalcedony quartz with a fine texture and parallel bands of alternate colors. This gem's name comes from the Greek word onyx which means fingernail or claw. Legend says that one day while the goddess Venus was sleeping, Cupid cut her fingernails and left the clippings scattered on the ground. Because no part of a heavenly body can die, the gods turned them into a gem, which later became known as onyx.
Alternate
Names
Black Chalcedony
Colors
Black

Black Onyx Classification

Common Name

Black Onyx

Species

Quartz

Variety

Chalcedony

Colors

Black

Alternate Names

Black Chalcedony

Gemstone Groups

Key Separations

RI, SG, appearance and fracture

Comments

Gray chalcodony that has been boiled in a sugar solution then exposed to sulphuric acid to produce black color.

Black Onyx Optical Properties

Transparency

Semitransparent - Semitranslucent

Refractive Index

1.539-1.535

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

Black Onyx Chemistry & Crystallography

Chemical Name

silicon dioxide (aka silica)

Chemical Formula

SiO2

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Aggregate

Comments

Black Onyx Characteristic Physical Properties

Hardness

6.5-7

Streak

White

Specific Gravity

2.55-2.7 Typical:2.6

Toughness

Excellent

Inclusions

Luster

Vitreous

Stability

Good

Fracture

Conchoidal, Granular

Cleavage

None

Comments

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