Ancylite is a group of hydrous strontium carbonate minerals containing cerium, lanthanum and minor amounts of other rare-earth elements. The composition is Sr(Ce,La)(CO3)2(OH)·H2O with ancylite-Ce enriched in cerium and ancylite-La in lanthanum.[1][2]

Ancylite
Nenadkevichite-Ancylite-20236.jpg
Nenadkevichite with ancylite crystals on the side
General
CategoryCarbonate mineral
Formula
(repeating unit)
Sr(Ce,La)(CO3)2(OH)·H2O
Strunz classification5.DC.05
Dana classification16b.1.1.1
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPmcn
Identification
ColorLight yellow, orange-yellow, yellow-brown, grey
CleavageNone
FractureSplintery
TenacityBrittle
Mohs scale hardness4–4.5
LusterDull
StreakWhite
DiaphaneityTranslucent
Density3.95 g/cm3

Ancylite was first described in 1899 for an occurrence in the Narsarsuk pegmatite in west Greenland and named from the Greek αυκιλος for curved in reference to its rounded or distorted crystal form.[1][3]

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