Dendritic Sandstone Pendant
Dendritic Sandstone Pendant
Though they may look like fossil plants, dendrites are incredible and inorganic formations that occur solely due to interactions between physics and geochemistry. These branching patterns are made of manganese oxides and commonly form on the surface of sandstones. As the manganese cools, it crystalizes into thin, tree-like shapes in the same process that creates snowflakes.
This necklace is a sandstone pendant that has been imprinted with a manganese oxide dendrite in a branching pattern.
Dendritic Crystal Necklace
Dendrites are an incredible and completely natural formation of branching lines and colors. These "branches" are not fossils, but a geologic phenomena. When a mineral is supercooled, it can crystalize on the molecular level into symmetrical patterns. Sometimes, these patterns grow to be visible to the human eye, which we call dendrites.
When anchored around an inclusion, the supercooled material can grow outward in symmetrical but interrupted patterns. This is what gives a dendrite its iconic branches. Another great example is a snowflake, which is actually a dendritic ice crystal.
This specimen is a sandstone pendant which has been imprinted with a manganese dendrite. Branching patterns come in a variety of shapes and colors from black, brown, and orange. These particular dendrites come from Central Europe and measure about 1 to 1.5 inches long.
The pendants can appear as oval, triangular, and teardrop shapes and are set into a fine sterling sliver backing as well as an 18 inch chain. An informational card which serves as certificate of authenticity is also included.
MORE ABOUT DENDRITES
Our collection contains many fossils in a variety of patterns, colors, and ages. This dendrite, however, is not a fossil. Despite its plant-like appearance, it is a completely inorganic crystal formed through natural mechanisms of physics and geochemistry. Commonly mistaken for fossilized plants, dendrites are actually branching patterns of manganese oxide which have crystalized in unique formations.
Dendrite crystals often appear in sandstone or limestone. These porous rocks are perfect for manganese rich water to travel through, which deposits the mineral within the stone. The manganese then crystallizes well below its solidification point, due to a process called supercooling. The process occurs quite quickly and can cause the crystals to split off and grow outwards in thin branching patterns.
These crystals grow until temperature conditions change again, allowing more water to seep and more crystals to then grow, hence the phenomenon’s fractal nature. Over time, the manganese deposits grow in size until they are visible on the stone's surface.
Since this process occurs between rock layers, dendrite crystals are easy to identify and recover, hence their abundant appearance in fossil digs. That also means that they are often confused with fossilized plants. An expert can tell them apart at a glance, but a good rule of thumb is to see if any of the "branches" overlap with one another. A fossil plant may have fallen into the mud and twisted over itself, where a dendrite grows horizontally and rarely intersects.
This phenomenon also appears in many other places, from snowflakes to cooling molten metal. You might even notice it in the frost patterns on your window on a winter morning! ❄️
McKeown, David A., and Jeffrey E. Post. “Characterization of Manganese Oxide Mineralogy in Rock Varnish and Dendrites Using X-Ray Absorption Spectroscopy.” American Mineralogist, vol. 86, no. 5-6, 2001, pp. 701–713., https://doi.org/10.2138/am-2001-5-611.
Potter, Russel M., and Rossman, George R. "Mineralogy of manganese dendrites and coatings." American Mineralogist, Vol 64, 197, pp. 1219-1226.
“Dendritic Growth in Crystals.” Sandatlas, https://www.sandatlas.org/dendritic-growth-in-crystals/.
Wilson, Mark. “Wooster's Pseudofossil of the Week: Manganese Dendrites from Germany.” Wooster Geologists, 20 Jan. 2013, https://woostergeologists.scotblogs.wooster.edu/2013/01/20/woosters-pseudofossil-of-the-week-manganese-dendrites-from-the-germany/.