metamorphic
Petrified Wood
Silicified Wood (SiO2)
Hardness: 6.5–7 on Mohs scale. Color: Tan, brown, and reddish-brown due to iron impurities. Luster: Vitreous to dull. Structure: Microcrystalline (Cryptocrystalline) quartz, often retaining visible wood grain and bark textures. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.
- Hardness
- 6
- Color
- Tan, brown, and reddish-brown due to iron impurities
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5–7 on Mohs scale. Color: Tan, brown, and reddish-brown due to iron impurities. Luster: Vitreous to dull. Structure: Microcrystalline (Cryptocrystalline) quartz, often retaining visible wood grain and bark textures. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.
Formation & geological history
Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while buried under sediment. This typically occurs in ancient river deltas, floodplains, or volcanic ash deposits dating from the Devonian to the Holocene periods.
Uses & applications
Used primarily in lapidary work for making jewelry (cabochons), furniture (tabletops), and as decorative display specimens for collectors and interior design.
Geological facts
Specifically, these fossils are formed in anaerobic conditions that prevent wood rot before minerals can seep in. The colors are determined by trace elements: iron produces reds and yellows, manganese produces pinks or oranges, and copper or chromium produces greens.
Field identification & locations
Identify in the field by looking for rock fragments that exhibit growth rings, knot structures, or bark-like textures despite having the weight and hardness of stone. Common in the Western United States, particularly Arizona's Petrified Forest National Park.
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