🦴 Fossils
A fossil is a trace of ancient life preserved in rock. Collectors' favourites range from coiled ammonites and trilobites to petrified wood, Petoskey stones and insects trapped in amber.
Burial
An organism, shell or tree is buried quickly in mud, sand, volcanic ash or resin, before it can rot or be scavenged.
Permineralization
Groundwater carries dissolved silica, calcite or pyrite into the pores, which slowly fill up. Petrified wood, Petoskey stones and agatized coral form this way.
Replacement
The original material dissolves away and minerals take its place, sometimes copying details down to the cell. Opalized and pyritized fossils are examples.
Preservation
Hard parts such as teeth, bone and calcite shells can survive almost unchanged. Tree resin can harden into amber around an insect.
Fossilized corals · Marine fossils · Plant fossils · Other fossils
Ages are typical ranges for commonly collected material. Fossil collecting is regulated in many places: buy from reputable dealers and check local rules before you collect.
🪸 Fossilized corals
Corals have built reefs for over 450 million years. Rugose ('horn') and tabulate ('honeycomb' and 'chain') corals died out at the end of the Permian; their calcite skeletons survive in limestone, or were replaced by chalcedony to become agatized coral.
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🐚 Marine fossils
Most fossils come from the sea, where shells, teeth and skeletons were quickly buried in mud and sand. This section covers echinoderms (sea urchins, sand dollars, starfish, crinoids and blastoids), shark teeth, mollusks such as snails, clams and ammonites, and other ancient sea life.
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🌿 Plant fossils
Coal-swamp plants of the Carboniferous: giant scale trees, their roots and tree-sized horsetails, preserved in shale and sandstone.
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🦴 Other fossils
Fossil wood, bone and resin, plus gem-quality fossils.
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