Rock Identifier
Petrified Wood (Silicified Wood (SiO2 - Quartz/Chalcedony replacement)) — Mineral / Fossil
Mineral / Fossil

Petrified Wood

Silicified Wood (SiO2 - Quartz/Chalcedony replacement)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on the Mohs scale. Color: Brown, tan, and gray bands. Luster: Waxy to dull. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.

Hardness
6
Color
Brown, tan, and gray bands
Luster
Waxy to dull
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Physical properties

Hardness: 6.5–7 on the Mohs scale. Color: Brown, tan, and gray bands. Luster: Waxy to dull. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.

Formation & geological history

Formed through permineralization, a process where organic material is replaced by silica-rich water over millions of years, often in volcanic ash deposits. Common specimens range from the Triassic (225 million years) to the Pliocene.

Uses & applications

Used for lapidary work, jewelry, home decor (tabletops, bookends), and as highly sought-after geological collectibles.

Geological facts

Petrified wood is a fossil in which all the organic materials have been replaced with minerals while retaining the original structure of the wood, including growth rings and cellular detail. It is the state gem of Washington and the state fossil of Arizona.

Field identification & locations

Identify by looking for wood-like grain patterns, tree rings, and bark-like textures on the exterior. It is commonly found in badlands, desert regions, and areas with historic volcanic activity like the Southwest USA and Madagascar.

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Other mineral / fossil specimens

Petrified Wood / Fossilized Bone (Silicified / Mineralized Fossil (Silica SiO2)) — fossil

Petrified Wood / Fossilized Bone

Silicified / Mineralized Fossil (Silica SiO2)

fossil
Fish Fossil in Limestone (Lycoptera (likely) in Micritic Limestone) — sedimentary

Fish Fossil in Limestone

Lycoptera (likely) in Micritic Limestone

sedimentary
Weathered quartz-rich rock or fossil fragment (Indeterminate; likely quartz-bearing sandstone or siliceous fossil material) — mineral

Weathered quartz-rich rock or fossil fragment

Indeterminate; likely quartz-bearing sandstone or siliceous fossil material

mineral
Weathered quartz-rich rock fragment (Likely quartz-bearing sandstone or granitic rock; exact identification is uncertain from the image) — mineral

Weathered quartz-rich rock fragment

Likely quartz-bearing sandstone or granitic rock; exact identification is uncertain from the image

mineral
Likely weathered iron-rich pebble (brown sandstone or ironstone) (Indeterminate ferruginous sandstone/ironstone; commonly quartz (SiO₂) with iron oxides such as goethite and hematite) — sedimentary

Likely weathered iron-rich pebble (brown sandstone or ironstone)

Indeterminate ferruginous sandstone/ironstone; commonly quartz (SiO₂) with iron oxides such as goethite and hematite

sedimentary
Light-gray river pebble (Indeterminate; likely fine-grained quartz-rich rock such as quartzite or pale granite) — igneous

Light-gray river pebble

Indeterminate; likely fine-grained quartz-rich rock such as quartzite or pale granite

igneous