Modern shark teeth typically appear white or off-white, while fossilized teeth often display a wide array of shades, including black, brown, gray, and even more vibrant hues like blue, green, red, or orange. This difference in coloration is attributed to their distinct compositions and the geological processes they undergo over time.
The Natural Color of Modern Shark Teeth
Modern shark teeth are generally white or off-white due to their unique biological composition. The outer layer of a shark’s tooth is made of a hard, mineral-rich substance called enameloid, which is primarily composed of fluoroapatite. Beneath this outer layer lies dentin, a bone-like matrix that forms the tooth’s inner core. The high mineral content of fluoroapatite in the enameloid contributes significantly to the tooth’s opaque, light appearance.
Sharks continuously replace their teeth throughout their lives. They lose and replace teeth frequently, sometimes as often as once a week, with some species shedding a tooth in as little as 24 hours. This rapid turnover means that individual teeth do not remain in the shark’s mouth for extended periods. The constant replacement cycle prevents teeth from accumulating stains or significant discoloration. Sharks can shed tens of thousands of teeth over their lifetime, ensuring a continuous supply of sharp, functional teeth.
Their teeth are embedded in cartilage, not bone, which facilitates this rapid replacement system. This biological mechanism ensures that modern shark teeth maintain their natural, light coloration. The teeth are not exposed to the long-term environmental interactions that would lead to changes in their appearance.
The Colors of Fossilized Shark Teeth
Fossilized shark teeth are renowned for their diverse range of colors, which can include black, brown, gray, red, orange, blue, and green. These varied colors are not inherent to the living shark but are a direct result of the fossilization process, which occurs over thousands to millions of years. When a shark tooth is shed and settles on the seafloor, it must be rapidly buried by sediment to begin the fossilization process. This quick burial protects the tooth from decay caused by oxygen and bacteria.
The transformation into a fossil occurs through a process called permineralization. As water seeps through the overlying sediments, it carries dissolved minerals into the porous structure of the tooth. These minerals gradually fill in the microscopic pore spaces within the original tooth material, and over vast stretches of time, they replace the organic components. The specific minerals present in the surrounding sediment are the primary determinant of the fossilized tooth’s final color.
For example, teeth fossilized in sediments rich in iron compounds, iron sulfides, or manganese dioxide often turn black or dark gray. Organic-rich or peat-rich environments can also cause these dark colors. Conversely, iron oxides or tannins from decayed vegetation can impart brown, tan, red, or orange hues. Clay-rich or desert environments might lead to lighter, tan teeth. Rarer colors like blue or green can emerge from trace minerals such as copper; teeth preserved in sediments with fewer impurities, such as calcium carbonate or phosphate, may retain a lighter gray or even white appearance.