Ancylite

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.^[2][3]

Ancylite
Nenadkevichite with ancylite crystals on the side
General
Category	Carbonate mineral
Formula	Sr(Ce,La)(CO3)2(OH)·H2O
IMA symbol	Anc[1]
Strunz classification	5.DC.05
Dana classification	16b.1.1.1
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pmcn
Identification
Color	Light yellow, orange-yellow, yellow-brown, grey
Cleavage	None
Fracture	Splintery
Tenacity	Brittle
Mohs scale hardness	4–4.5
Luster	Dull
Streak	White
Diaphaneity	Translucent
Density	3.95 g/cm3

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.^[2][4]