Where is Shale with Dendrites found?
Shale (sedimentary rock) with Manganese Oxide Dendrites
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Open the appShale with Dendrites occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Shale with Dendrites
Worldwide
Manganese dendrites can be found in shales and other fine-grained sedimentary rocks globally, as the conditions for their formation are not geographically restricted. Specific notable occurrences are less about specific localities and more about the presence of suitable host rocks and geochemical conditions.
United States
Commonly found in various shale formations across the US, particularly in areas with exposed sedimentary sequences. For example, in parts of the Appalachian Basin, Rocky Mountains, and Midwestern states.
Europe
Reported from numerous European countries with extensive sedimentary rock exposures, including the UK, Germany, France, and Italy.
Collecting tips
- Look for Exposed Shale Outcrops. Search for road cuts, stream beds, quarries, and other areas where shale layers are exposed. Weathering can sometimes highlight the dendritic patterns.
- Examine Bedding Planes and Fracture Surfaces. Dendrites typically form on these surfaces. Carefully split shale layers along their natural fissility to reveal potential patterns.
- Distinguish from Fossils. Remember that dendrites are mineral growths, not organic remains. They lack the cellular structure or three-dimensional relief often seen in true plant fossils. The patterns are typically flat and two-dimensional.
- Carry a Hand Lens. A hand lens (10x magnification) can help in examining the intricate details of the dendritic patterns and confirming their mineralogical nature.
Quick Check
- Color:
- Dark gray to black shale with black, fern-like patterns.
- Luster:
- Dull to earthy for shale, submetallic for dendrites.
- Streak:
- Shale: typically white, gray, or brown (depending on composition). Dendrites (manganese oxides): black to brownish-black.
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