Outstanding white sharp crystals of the extremely rare Ba-Ca carbonate mineral paralstonite from the type locality in Minerva mine Illinois (Minerva #1 Mine, Cave-in-Rock, Hardin County, Illinois, United States of America). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Paralstonite
Paralstonite is an IMA-recognized mineral species in the carbonate class, with the chemical formula BaCa(CO₃)₂.
It crystallizes in the hexagonal crystal system (space group P321). It is a member of the Paralstonite structural group.
Key properties: Mohs hardness 4–4.5; specific gravity 3.6; White streak; Vitreous luster; optically uniaxial.
IMA symbol Pasn, IMA status: approved, named in 1978.
A rare mineral found in low-temperature hydrothermal Pb–Zn deposits.
It is found associated with Calcite, alstonite, fluorite, sphalerite (Minerva No. 1 mine, Illinois, USA); olekminskite, calcite, barite, ankerite, ancylite-(Ce), narsarsukite, sphalerite.
Its name comes from the Greek for near and its morphological and chemical relation with alstonite.