Ancylite-(La)
Ancylite is a group of hydrous strontium carbonate minerals containing cerium, lanthanum and minor amounts of other rare-earth elements. The chemical formula is Sr(Ce,La)(CO3)2(OH)·H2O with ancylite-Ce enriched in cerium and ancylite-La in lanthanum. Ancylite was first described in 1899 for an occurrence in the Narsarsuk pegmatite in west Greenland and named from the Ancient Greek: ἀγκύλος for curved in reference to its rounded or distorted crystal form.
Intro adapted from Wikipedia (CC BY-SA).
Ancylite-(La) is an IMA-recognized mineral species in the carbonate class, with the chemical formula LaSr(CO₃)₂(OH)·H₂O.
It crystallizes in the orthorhombic crystal system (space group Pmcn). It is a member of the Ancylite structural group.
Key properties: Mohs hardness 4–4.5; specific gravity 3.69; White streak; Vitreous luster; optically biaxial.
IMA symbol Anc-La, IMA status: approved, named in 1995.
A rare mineral found in nepheline syenites in differentiated alkalic massifs.
It is found associated with Aegirine, astrophyllite, loparite-(Ce), donnayite-(Y), belovite-(Ce), kukharenkoite-(Y), nenadkevichite, “biotite”, eudialyte, catapleiite, apophyllite.
The name refers to its relation to ancylite-(Ce) and its dominant content of lanthanum.