Petrified wood, Triassic, Chinle formation, Arizona

This fossil was part of a tree more than 200 million years ago. A solution of silica (the oxide of silicon) seeped into the fallen log and permeated its cells, crystallizing into quartz and eventually producing petrified wood. In this specimen, limonite (an iron oxide) contributes to the bright central arc, while fine spherules of hematite (another iron oxide) suffuse the quartz with a purplish hue. Hematite also yields the red bordering the yellow.

Tree-fern stem, Jurassic, Lune River, Tasmania, Australia

In a partial cross section of a tree fern that lived about 200 million years ago, blue chalcedony (a type of quartz) and orange iron oxides and hydroxides have replaced the original structures. The area at the top was once bundles of wood cells, the circles at the bottom were leaf bases, and the tiny rounded shapes were roots.

Stromatolite, Precambrian, Bristol, England

Cyanobacteria formed mats in shallow seas billions of years ago. Their blue-green pigmentation made photosynthesis possible, thereby adding significant quantities of oxygen to Earth's early atmosphere. In this 2.5-billion-year-old specimen, sand was entrapped in the folds of the mats when they were buried by carbonate sediments.

Chancelloria, Middle Cambrian, Wheeler Shale formation, Utah

Chancelloria, a small invertebrate that lived on the seafloor 500 million years ago, captured prey by using its supple body as a net. Brown, many-armed iron oxide stars embedded in an azure matrix of slate were once the creature's cells.

Pentoxylon, Jurassic, Miles, Australia

A tree with long leaves on short stalks, Pentoxylon was unlike any tree known today. Its fossilized pollen resembles that of ginkgoes and cycads. Columns of vascular tissue are visible here in a cross section of trunk. The colors of the chert (the variety of quartz that has replaced the wood) are imparted primarily by iron oxides.

Ammonite, Upper Cretaceous, Bear Paw formation, Alberta, Canada

Ammonites — mobile marine predators with spiral shells resembling those of the modern nautilus — thrived for millions of years before disappearing, along with the large dinosaurs, 65 million years ago. The evenly spaced layers of shell at the molecular level diffract light to produce this fossil's iridescence.

Gomphotheriid tooth, Oligocene, Montana

Early relatives of modern elephants, with shorter trunks and elongated jaws bearing shovel-like incisors, gomphotheriids thrived about 30 million years ago, although some members of the group persisted until much later. This polished section of a tooth crown reveals figure-eight patterns of the blue mineral vivianite, a phosphate of iron.

Coral, Lower Pleistocene, Caloosahatchee formation, Florida

This piece of a coral colony's calcium carbonate skeleton, from a long-vanished lagoon near what is now Florida's Gulf Coast, has been preserved for about 1.5 million years. Corals like these have altered little since their origin in the Triassic, about 230 million years ago.

Dinosaur bone, Jurassic, Morrison formation, Colorado

In the spongy interior of a dinosaur bone, the surfaces of the chambers between the bone spikules incorporated iron oxides after undergoing structural change. Later these chambers filled with blue-gray agate. Concentric circles mark the growth periods of the agate crystals.

Giraud Foster and Norman Barker have worked together for twelve years, using light-scanning macrographic equipment of their own design to capture the rich patterns and colors of fossilized organisms. Foster lives in Baltimore and is a physician, biochemist, archaeologist, and gourmet chef. Barker, a six-time winner of Nikon’s Small World Competition, is an assistant professor of pathology and arts as applied to medicine at the Johns Hopkins University, where he also runs the photography laboratory. The two men—who use a Hasselblad camera mounted on a heavy monorail base, macro lenses, and Ektachrome EPP film for their fossil photographs--share a passion for the “shouts of vivid color, twists and convolutions, and geometric patterns” of fossils. Eighty of their images will appear in Ancient Microworlds, scheduled for publication this fall.

Copyright © 2000 American Museum of Natural History

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