The charoitite of the Sirenevy Kamen (“purple stone”) deposit of eastern Siberia is thought to have formed when an alkali syenite intrusion encountered a dolomite containing a significant amount of terrigenous clastic sediment. The result was a complex geochemical environment of hydrothermal metasomatism.

Mineral-rich fluids permeated the dolomite and surrounding rocks, forming charoite and a variety of other rare minerals with complex chemical compositions. The charoite in these rocks is impure and intimately mixed with microscopic particles of other rare minerals (see accompanying photomicrograph).