Hydroterskite
A rare zirconium silicate related to terskite, discovered in the Saint-Amable sill near Montréal.
Intro adapted from Wikipedia (CC BY-SA).
Hydroterskite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₂ZrSi₆O₁₂(OH)₆.
It crystallizes in the orthorhombic crystal system (space group Pnca). It is a member of the Terskite structural group.
Key properties: specific gravity 2.57; White streak; Vitreous luster; optically biaxial.
IMA symbol Hter, IMA status: approved, named in 2015.
Formed in cavities in a phonolite sill, by post-magmatic hydrothermal processes.
It is found associated with Manganoneptunite, aegirine, analcime, an astrophyllite-group mineral, catapleiite, a eudialyte-group mineral, fluorite, monazite, natrolite.
The name refers to the mineral’s essential water (hydroxyl) and relation to terskite.