Dendrite (crystal) - Mineralogy and Paleontology

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 (Na₄Mn₁₄O₂₇·9H₂O)
• coronadite (PbMn₈O₁₆)
• cryptomelane (KMn₈O₁₆)
• hollandite (BaMn₈O₁₆)
• romanechite ((Ba,H₂O)Mn₅O₁₀)
• todorokite ((Ba,Mn,Mg,Ca,K,Na)₂Mn₃O₁₂·3H₂O) and others.

A three-dimensional form of dendrite develops in fissures in quartz, forming moss agate.