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Amber, an organic gemstone, is the fossilized resin of prehistoric trees which grew up to 50 million years ago. The stone has been used for jewelry since the time of Christ. The world's finest amber comes from the region around the Baltic sea. Ammonite is the fossilized shell of ancient sea amminoids and nautiloids, ancestors of the present-day pearly nautilus. An ammonite fossil formed when the ammonite shell absorbed minerals from silt. Centuries of sediment layers compressed the minerals to rock. Orthoceras are prehistoric cephalopods related to the modern day squid, cuttlefish, and octopus. They date back about 350 million years and many are found in the Moroccan Sahara Desert. Prehistoric sharks' teeth may be black, brown, or gray, depending on the minerals in the soil in which they have been buried. Sand at the bottom of the ocean preserved and fossilized the teeth, and wave action uncovers and washes them ashore. Many fossil shark teeth have been collected from the coastal areas of the Gulf of Mexico. Trilobites were ancient sea-dwelling arthropods that lived in shallow coastal areas. They survived for approximately 350 million years beginning in the Cambrian period and are the earliest animal to exhibit evidence of eyesight in the fossil record.
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