Most "is this a fossil" questions come down to a handful of checks anyone can do in the field with no equipment beyond a hand lens.
Check the rock type first
Fossils only occur in sedimentary rock. If the rock is hard, crystalline, glassy, or clearly volcanic in origin, whatever pattern you are seeing is not a fossil, no matter how organic it looks. See what rocks should I look for when fossil hunting for how to recognise sedimentary rock in the first place.
Look for biological symmetry and repetition
Fossils tend to show patterns that pure geology rarely produces on its own: bilateral symmetry, evenly spaced segments, spiral growth, or a consistent internal structure repeated across the specimen. Random mineral banding, crystal growth, and erosion marks are usually irregular or follow the physics of fracturing and flow rather than a body plan.
Use texture and a hand lens
At 10x magnification, fossilised bone typically shows a fine internal spongy or fibrous texture, distinct from surrounding rock. Shell fossils often retain faint growth lines. Pseudofossils — mineral formations that mimic biological shapes, like dendrites (branching mineral deposits that look like plants) or concretions (rounded nodules with no internal structure) — usually fail this closer look, showing crystalline or uniformly structureless material instead.
Common look-alikes worth knowing
- Dendrites — black, fern-like mineral growths on rock surfaces, frequently mistaken for plant fossils. They are flat surface deposits, not impressions with any depth.
- Concretions — rounded, layered mineral nodules that can resemble eggs or bones but split to reveal uniform mineral fill, not internal biological structure.
- Liesegang rings — banded mineral patterns that can look like tree rings or shell growth lines but form from chemical diffusion, not biology.
When it is still ambiguous
Photograph it well and check an identification app or forum — see free apps to identify fossils you found — and if it still seems significant, a local museum or geology department can usually settle it definitively from a good photo.