Chemistry:Ilvaite

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Ilvaite
Ilvaite-es111c.jpg
General
CategorySorosilicates
Formula
(repeating unit)
Ca(Fe2+)2Fe3+[O|OH|Si2O7]
Strunz classification9.BE.07
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/a
Identification
Mohs scale hardness5.5–6.0
Streakblack
Specific gravity3.8–4.1

Ilvaite is a sorosilicate of iron and calcium with formula: CaFe2+2Fe3+Si2O7O(OH). Both manganese and magnesium substitute in the structure. Ilvaite crystallizes in the monoclinic system in black prismatic crystals and columnar masses. It is black to brownish black to gray and opaque. It has a Mohs hardness of 5.5 to 6 and a specific gravity of 3.8 to 4.1. Ilvaite is structurally related to lawsonite.

It occurs in contact metamorphic rocks and skarn ore deposits. It also occurs less commonly in syenites.

Ilvaite was first described in 1811 on the island of Elba and the name ilvaite from the Latin name Ilva of the island. Sometimes referred to as yenite.

References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode2021MinM...85..291W.