and 48 hours) and replaced with new teeth. Different limpet species exhibit different overall shapes of their teeth. Growth and development Development of limpet teeth occurs in conveyor belt style, where teeth start growing at the back of the radula, and move toward the front of this structure as they mature. The growth rate of the limpet's teeth is around 47 hours per row. Fully mature teeth are located in the scraping zone, the very front of the radula. The scraping zone is in contact with the substrate that the limpet feeds off of. As a result, the fully mature teeth are subsequently worn down until they are discarded – at a rate equal to the growth rate. To counter this degradation, a new row of teeth begin to grow. Biomineralization Currently, the exact mechanism behind the biomineralization of limpet teeth is unknown. However, it is suggested that limpet teeth biomineralize using a dissolution-reprecipitation mechanism. Specifically, this mechanism is associated with the dissolution of iron stored in epithelial cells of the radula to create ferrihydrite ions. These ferrihydrite ions are transported through ion channels to the tooth surface. The build-up of enough ferrihydrite ions leads to nucleation, the rate of which can be altered via changing the pH at the site of nucleation. After one to two days, these ions are converted to goethite crystals. The unmineralized matrix consists of relatively well-ordered, densely packed arrays of chitin fibers, with only a few nanometers between adjacent fibers. The lack of space leads to the absence of pre-formed compartments within the matrix that control goethite crystal size and shape. Because of this, the main factor influencing goethite crystal growth is the chitin fibers of the matrix. Specifically, goethite crystals nucleate on these chitin fibers and push aside or engulf the chitin fibers as they grow, influencing their resulting orientation. Strength Looking into limpet teeth of Patella vulgata, Vickers hardness values are between 268 and 646 kg⋅m−1⋅s−2, while tensile strength values range between 3.0 and 6.5 GPa. As spider silk has a tensile strength only up to 4.5 GPa, limpet teeth outperforms spider silk to be the strongest biological material. These considerably high values exhibited by limpet teeth are due to the following factors: The first factor is the nanometer length scale of goethite nanofibers in limpet teeth; at this length scale, materials become insensitive to flaws that would otherwise decrease failure strength.