Mineral Information and Data:

Opal
SiO2 • nH2O [CNMNC approved formula]

Named From the Old Indian upala - "precious stone.".

IMA status : Valid species (Pre-IMA) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
75.02.01.01  
  (75) Tectosilicate Si Tetrahedral Frameworks
  (75.02) with H2O and organics
  (75.02.01)
  
Nickel-Strunz
(10th edition) :
04.DA.10
  (04) Oxides and Hydroxides
  (04.D) Metal:Oxygen = 1:2 and similar
  (04.DA) With small cations: Silica family
  
Crystal system: Amorphous — no crystals
Point group (H-M): none — no crystals
  
  
  
Other Properties: BioMineral.

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