Prootonite

Prootonite is a fictional mineral commonly used in teaching and speculative mineralogy to illustrate the interplay of phosphate and sulfide chemistries in a solid solution. It is described as a sulfide-phosphate solid solution with a layered or framework-like structure that can support proton conduction in theory.

Most descriptions portray prootonite as containing calcium and sodium among major cations, with phosphate groups arranged in a framework interleaved with sulfide layers. The composition is variable, allowing substitutions by iron or magnesium in trace amounts, resulting in a solid solution series.

Prootonite is reported to occur as dark gray to brown crystals with a vitreous to pearly luster. Hardness is commonly given as 4 to 6 on Mohs scale, with a brittle fracture and a white to pale gray streak. Cleavage is imperfect, reflecting its layered structure.

In fictional contexts, prootonite forms in hydrothermal veins where phosphate-rich fluids interact with metallic sulfide-bearing rocks under reducing conditions. It is often described as coexisting with apatite, pyrite, and magnetite, and is said to be more stable at elevated temperatures and pressures typical of deep crustal environments.

Because of its proposed proton-conducting properties, prootonite is used in model discussions of solid-state electrolytes and as a teaching example of how crystal structure influences transport phenomena. No natural occurrence or commercial use is established; it remains a construct for conceptual exploration.