Mineral Information and Data:

Afwillite
Ca3(SiO3)2(OH)2 • 2H2O [CNMNC approved formula]

Named for Alpheus Fuller Williams (1874-1953), General Manager, DeBeers Consolidated Mines, Kimberley, South Africa.

IMA status : Valid species (Pre-IMA 1925) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
52.04.07.01  
  (52) Nesosilicate Insular SiO4 Groups and O, OH, F, and H2O
  (52.04) with cations in [6] and/or > [6] coordination
  (52.04.07) No group assigned
  
Nickel-Strunz
(10th edition) :
09.AG.75
  (09) Silicates
  (09.A) Nesosilicates (Isolated tetrahedron) structures
  (09.AG) Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination
  
Crystal system: Monoclinic System
Point group (H-M): m — domatic
Unit cell: a = 16.278 Å, b = 5.632 Å, c = 13.536 Å, b = 134.9°
Crystal Habit: Crystals elongated, tabular; massive, often striated, radial fibrous spherulites
  
Color: Colorless or white
Diaphaneity: Transparent
Luster: Vitreous
Hardness (Mohs): 3 - 4
Measured Density: 2.630 g/cm3
Cleavage: 2; {101} perfect; {100} good
Tenacity: Brittle
Fracture: Conchoidal
Streak: White
  
Geologic Setting: A product of contact metamorphism of limestones.
Mineral Association: Apophyllite, natrolite, thaumasite, merwinite, spurrite, gehlenite, ettringite, portlandite, hillebrandite, foshagite, brucite, calcite.
  

 

Afwillite
Crystallized afwillite prisms.
Origin: Wessels Mine, Kalahari Manganese Field,
Northern Cape Province, South Africa.
Sample size: Crystal size 1.5 mm
Photo: John Veevaert, Trinity Mineral Co

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