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Dendrites get their names from their branching, tree-like pattern.
These are pseudofossils - a naturally occurring growth of minerals (iron/manganese) that takes the appearance of a fossil plant. I collected these from a roadside cutout of limestone.
Mineral tree Mineral bearing fluids often pass through rocks, sometimes leaving behind a little parting gift on their way. This happens when the fluids encounter different conditions, including both physical ones such as pressure/temperature and chemical conditions such as acidity or the oxidising/reducing potential of the rocks themselves. The fluids often leach elements out of the rocks, leaving others behind in a complex series of chemical reactions usually placed under the umbrella term hydrothermal alteration, that covers a huge range of transformations dependent on the nature of the interacting rocks and fluids. In this case, dendritic veins of the manganese mineral pyrolusite have been precipitated along networks of microcracks as the fluids pass through, leaving behind these beautiful arborescent mineral formations. Loz Image credit: Aram Dulyan
Dendritic agate.
Like some mysterious Carboniferous ferns, a pattern of metal oxide, probably manganese, has infiltrated into this cream coloured agate, either during or shortly after formation when the silica was still in a gel form. Such plant or landscape patterns are highly sought after by collectors, and usually are full of rich detail when examined under a hand lens.
Loz
Image credit: Chip Clarke
17.01.2017 Canadian Museum of Nature - Geology Exhibit
Manganese Dendrites on Limestone
Locality: Solnhofen, Bavaria, Germany
PYROLUSITE (Manganese Dioxide) from Imini Mine, Quarzazate Province, Morocco. Photo shows opened pyrolusite nodule with acicular crystal habit at the edges of the nodule.
Mineral tree Mineral bearing fluids often pass through rocks, sometimes leaving behind a little parting gift on their way. This happens when the fluids encounter different conditions, including both physical ones such as pressure/temperature and chemical conditions such as acidity or the oxidising/reducing potential of the rocks themselves. The fluids often leach elements out of the rocks, leaving others behind in a complex series of chemical reactions usually placed under the umbrella term hydrothermal alteration, that covers a huge range of transformations dependent on the nature of the interacting rocks and fluids. In this case, dendritic veins of the manganese mineral pyrolusite have been precipitated along networks of microcracks as the fluids pass through, leaving behind these beautiful arborescent mineral formations. Loz Image credit: Aram Dulyan
