How to Identify Petrified Wood

Start with the paradox that defines it: it looks like wood but behaves like stone. The single strongest clue is preserved tree anatomy in a rock-hard object — concentric annual growth rings, radial rays, and sometimes bark texture or knots frozen into the surface, exactly like the cream-and-tan piece here with its clear radiating rings. If you can see a wood-grain or growth-ring pattern in something that is unmistakably stone, you are almost certainly looking at petrified wood.

Confirm with weight and hardness. Petrified wood is dense and heavy for its size — noticeably heavier than a piece of timber the same size — because it is essentially quartz at roughly 2.5–2.7 g/cm³. Test the hardness: it sits at about 6.5–7 on the Mohs scale, so a steel knife or nail will not scratch it, and a sharp edge or corner of the specimen will readily scratch glass. Real wood, by contrast, is light, dents under a fingernail, and is easily cut. That hardness test alone separates petrified wood from carved or stained wood look-alikes.

Check the broken and polished surfaces. Where petrified wood is chipped or broken it shows a conchoidal (curved, glass-like) fracture typical of quartz, not the splintering break of wood. Polished faces take a high, glassy, almost gemlike luster and often reveal agate banding, translucency at thin edges, or sparkling crystalline pockets — features no real wood ever shows. Colors are earthy minerals (cream, tan, brown, red, yellow, sometimes black or green) laid into the grain rather than the uniform tone of a single wood species.

Use scent and feel as quick negatives. Petrified wood has no woody smell, does not warm up or feel 'grippy' like timber, and feels cold and slick like stone. Sanding or scratching it produces no wood scent and no fibrous dust — only fine mineral powder (which is a silica hazard; test wet or with protection).

The common confusions are with plain agate or jasper, with concretions or ordinary banded rock, and with real or resin-imitation wood. Featureless agate and jasper share the quartz hardness and polish but lack the growth-ring and cell structure — look specifically for parallel wood grain and concentric rings, which random agate does not have. Actual timber and wood-look resins or ceramics fail the hardness and weight tests instantly: they scratch, dent, and weigh far less. When a stony object combines quartz hardness, heavy heft, a glassy conchoidal break, and an unmistakable wood-grain ring pattern, petrified wood is the confident answer.