with and the width with . Therefore, growth mainly takes place at the tip the parabolic interface, which draws out longer and longer. Eventually, the sides of this parabolic tip will also exhibit instabilities giving a dendrite its characteristic shape. Preferred growth direction When dendrites start to grow with tips in different directions, they display their underlying crystal structure, as this structure causes the anisotropy in surface energy. For instance, a dendrite growing with BCC crystal structure will have a preferred growth direction along the directions. The table below gives an overview of preferred crystallographic directions for dendritic growth. Note that when the strain energy minimisation effect dominates over surface energy minimisation, one might find a different growth direction, such as with Cr, which has as a preferred growth direction , even though it is a BCC latice. Metal dendrites For metals the process of forming dendrites is very similar to other crystals, but the kinetics of attachment play a much smaller role. This is because the interface is atomically rough; because of the small difference in structure between the liquid and the solid state, the transition from liquid to solid is somewhat gradual and one observes some interface thickness. Consequently, the surface energy will become nearly isotropic. For this reason, one would not expect faceted crystals as found for atomically smooth interfaces observed in crystals of more complex molecules. Mineralogy and paleontology In paleontology, dendritic mineral crystal forms are often mistaken for fossils. These pseudofossils form as naturally occurring fissures in the rock are filled by percolating mineral solutions. They form when water rich in manganese and iron flows along fractures and bedding planes between layers of limestone and other rock types, depositing dendritic crystals as the solution flows through. A variety of manganese oxides and hydroxides are involved, including: birnessite () coronadite () cryptomelane () hollandite () romanechite () todorokite () and others. A three-dimensional form of dendrite develops in fissures in quartz, forming moss agate NASA microgravity experiment The Isothermal Dendritic Growth Experiment (IDGE) is a materials science solidification experiment that researchers use on Space Shuttle missions to investigate dendritic growth in an environment where the effect of gravity (convection in the liquid) can be excluded. The experimental results indicated that at lower supercooling (up to 1.3 K), these convective effects are indeed significant. Compared to the growth in microgravity, the tip velocity during dendritic growth under