Parakriinit

Parakriinit is a rare mineral species first described in 2023 from hydrothermally altered volcanic rocks of the Parakriin Formation in central Asia. The name is derived from the formation where it was discovered. It is characterized by a hydrated phosphate-silicate composition with calcium, aluminum, silicon, and trace rare-earth elements.

Idealized formula: CaNa(Al,Fe)Si2O7(OH)·nH2O. Crystal system monoclinic; habit prismatic to tabular crystals up to 3 mm; color pale green to olive; transparency translucent; luster vitreous. Mohs hardness 4.5–5.5; cleavage indistinct; fracture conchoidal to uneven.

Occurrence: Parakriinit occurs in hydrothermal veins within volcanic rocks, especially where phosphate-rich fluids interact with aluminosilicate hosts. Associated minerals include quartz, fluorapatite, and pyrite.

Structure and chemistry: X-ray diffraction identifies a framework of aluminosilicate chains with integrated phosphate groups; hydrated layers contribute to its stability. The mineral displays modest substitution of Si by Al and of Ca by Na.

Origin and classification: Parakriinit is commonly placed in the phosphate-silicate minerals group, with close relations to the apatite family and to certain aluminosilicates. It is distinguished by its hydration state and its characteristic phosphate-silicate framework.

Significance and studies: Due to its rarity, Parakriinit has limited industrial use but is of interest for studies on hydrothermal systems and mineral evolution. Ongoing work focuses on refining its structure, formula, and paragenesis.