Mineral Information and Data:

Ilvaite
CaFe3+Fe2+2O(Si2O7)(OH) [CNMNC approved formula]

Named from the Latin name, Ilva, for the Island of Elba, on which it was first found.

IMA status : Valid species (Pre-IMA 1811) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
56.02.03.03  
  (56) Sorosilicate Si2O7 Groups and O, OH, F. and H2O
  (56.02) with cations in [4] and/or >[4] coordination
  (56.02.03) Lawsonite - Ilvaite group
  
Nickel-Strunz
(10th edition) :
09.BE.07
  (09) Silicates
  (09.B) Sorosilicates (dimer) structures
  (09.BE) Si2O7 groups, with additional anions; cations in octahedral [6] and greater coordination
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Space group: Pbnm
Unit cell: a = 8.800 Å, b = 13.019 Å, c = 5.852 Å, Z=4
Crystal Habit: Crystals prismatic, striated || {001}, to 25 cm; columnar, radiating, or compact massive.
  
Color: Iron-black or dark grayish black
Diaphaneity: Opaque, translucent in fine fragments
Luster: Submetallic
Hardness (Mohs): 5.5 - 6
Measured Density: 3.99 - 4.05 g/cm3
Cleavage: Distinct on {001} and {010}
Tenacity: Brittle
Fracture: Uneven
Streak: Black, inclining to green or brown
  
Polymorphism and Series: Monoclinic forms are also known with Point Group: 2/m -prismatic ; Space group P21/a. Cell: a = 13.0103(5) b = 8.8039(4) c = 5.8517(3), β = 90:209(5)°: Z = 4
Geologic Setting: In contact metasomatic rocks and iron deposits; in metamorphosed limestones and dolostones with other calc-silicate minerals.
Mineral Association: Quartz, magnetite, hedenbergite, sphalerite, fluorite
  
Other Properties: Gemstone Unlikely Available.

 

Ilvaite
Origin: South Mountain District, Owyhee Co., Idaho, U.S.A.
Sample size: 4.1 x 3.0 x 2.4 cm
Photo: Rob Lavinsky

 

Ilvaite
(zoom-in of above)

 

Ilvaite
Origin: Dalnegorsk, Primorskiy Kray, Russia
Sample size: 6 x 5 x 5 cm
Photo: Rob Lavinsky

 

Ilvaite
(zoom-in of above)

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