Petrified Wood Gem Guide and Properties Chart

Petrified Wood

By Tim Matthews, JD, FGA, GG, DGA,
CEO and President of JTV (retired)

Published: June 2014

Modified: November 2023

Petrified wood is the fossilized remains of what once was wood. The material became petrified over time by the invasion of minerals into cavities between and within the cells of natural wood. Instead of decaying, the organic materials in the wood were replaced with minerals, primarily silicate of quartz, without changing the original structure of the wood.

General Information

Classification
Optical Properties
Characteristic Physical Properties
Chemistry & Crystallography

Common Name

Petrified Wood

Transparency

Translucent - Opaque

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

Inclusions

Petrified wood looks like a patterned jasper. Sometimes the structure of the original organic material is replicated when the quartz replaces the original material.

Luster

Vitreous, Greasy

Stability

Good

Fracture

Conchoidal, Granular

Cleavage

None

Chemical Name

silicon dioxide (aka silica)

Chemical Formula

SiO₂