Mineral Information and Data:

Ancylite-(La)
LaSr(CO3)2(OH) • H2O [CNMNC approved formula]

Named for the composition and from the Greek "curved," in allusion to the rounded and distorted character of the crystals.

IMA status : Approved Species 1997 (IMA1995-053)
CLASSIFICATION 
Dana
(8th edition) :
16b.01.01.05  
  (16b) Carbonates - Hydroxyl or Halogen
  (16b.01) where (A)m (B)n (XO3)p Zq, with (m+n):p=1:1
  (16b.01.01) Ancylite group
  
Nickel-Strunz
(10th edition) :
05.DC.05
  (05) Carbonates and Nitrates
  (05.D) Carbonates with Additional Anions, with H2O
  (05.DC) With large cations
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 5.072 Å, b = 8.589 Å, c = 7.276 Å
Crystal Habit: Crystals are dipyramidal {111}, with {120}, {101}, platy or short prismatic, faces typically curved, to 2 mm; in druses and uncommonly as skeletal or dendritic aggregates.
  
Color: Colorless, pale yellowish gray, yellowish brown, yellow; colorless to pale yellow in thin section.
Diaphaneity: Translucent
Luster: Vitreous
Hardness (Mohs): 4 - 4.5
Measured Density: 3.69 g/cm3
Tenacity: Brittle
Fracture: Conchoidal
Streak: White
  
Geologic Setting: A rare mineral in nepheline syenites in differentiated alkalic massifs.
Mineral Association: Aegirine, astrophyllite, loparite-(Ce), donnayite-(Y), belovite-(Ce), kukharenkoite-(Y), nenadkevichite, “biotite”, eudialyte, catapleiite, apophyllite, fluorapatite, calcite. (Mt. Kukisvumchorr, Kola Peninsula, Russia)
  

 

Ancylite-(La)
Beige-brown crystals of ancylite-(La) in matrix.
Origin: Mt. Aikuaivenchorr, Chibiny, Kola Peninsula, Russia
Sample size: 1.7 x 2.3 cm
Photo: Diederik Visser

 

Ancylite-(La)
Pale brown aggregates of ancylite-(La) crystals with some aegirine on matrix
Origin: Mt. Aikuaivenchorr, Chibiny, Kola Peninsula, Russia
Sample size: 2 x 3.5 cm
Photo: Diederik Visser

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