A removable steel armature holds vertebrae in Sue's tail.
Working under a microscope, a preparator removes matrix from a fossil.
|Pick and shovel work
Few fossils are shrink-wrapped, clean and neat, when discovered. Instead, they are often encased in sediment turned to rock -- matrix. Originally, fossils were removed from matrix with stone masons' tools -- think hammers and chisels -- then finer tools like dental picks. Preparing good specimens could take years with hand tools. And the tools threatened the fossils -- a misplaced blow could wreck the fragile old things.
Today, air-operated tools are augmenting hand tools. You're thinking jackhammers, we're actually talking a miniature version of a tool designed for industrial engraving. Air oscillates the piston at up to 40,000 strokes per minute. The piston moves a small tungsten-carbide cutting tool, which quickly dislodges whatever happens to be in its way.
The pneumatic tool is equally destructive of fossil or matrix, so you want practice, practice, practice, before you attack a valuable specimen like Sue. In fact, even the pros leave a thin veneer of matrix on the fossil, then remove it with a sandblaster.
Just like they remove graffiti from brick?
Almost. You could blast right through a fossil, even with the miniature sandblasters used in fossil labs. But controlling air pressure, abrasive, nozzle and technique, allows you to remove the matrix without touching the fossil.
Selecting abrasive is key: Instead of sand, fossil preparators use aluminum oxide -- for coarse removal -- and glass, powdered limestone, baking soda or even powdered cork -- for fine removal.
If power tools can't complete the job, preparators may return to their dental roots, and use dental picks or jewelers' tools to remove the last bits of matrix. (Fortunately, dinos don't scream in the dentist's chair! And you can forget about malpractice suits...)
99.44 percent pure
While many "fossils" on display are actually fakes (the real fossils being too valuable for display), the Field assures us that the T. rex on display is the real Sue -- all except for the bones that were never found, and the head, which was too heavy to hang on the skeleton. The 'ol noggin got its own display case.
What did we learn from Sue's skull?
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