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Ilvaite
Current inventory:  0 gems
 

Chemistry:  CaFe₂⁺² Fe³⁺OSi₂O₇(OH)
[Calcium Iron Silicate Hydroxide]

Discovered in 1811;   IMA status: Valid (pre-IMA; Grandfathered).
Ilvaite is named from the Latin name, Ilva, for the Island of Elba, on which it was first found.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/C.10-20

Nickel-Strunz 10th Ed. ID:

9.BE.07

9 : SILICATES (Germanates)
B : Sorosilicates
E : Si₂O₇ groups, with additional anions; cations in octahedral [6] and greater coordination

Related to:

Lawsonite - Ilvaite Series

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Crystals prismatic, to 25 cm; columnar, radiating, or compact massive.

Twinning:

None

Physical Properties

Cleavage:

[001] Distinct, [010] Distinct

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Hardness (Mohs):

5.5 - 6.0

Density:

3.99 - 4.05 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Iron Black, dark Grayish Black

Transparency:

Opaque; Translucent on thin edges

Luster:

Sub-Metallic

Refractive Index:

1.727 - 1.883  Biaxial ( + )

Birefringence:

0.1560

Dispersion:

Strong; r < v

Pleochroism:

Strong; X = dark green; Y = yellow-brown to dark brown; Z = dark brown

Anisotrophism:

Strong; color in reflected light: light gray to bluish gray, pinkish red to violet

Occurances

Geological Setting:

In contact metasomatic rocks and iron deposits; in metamorphosed limestones and dolostones with other calc-silicate minerals.

Common Associations:

Fluorite, Hedenbergite, Magnetite, Quartz, Sphalerite

Common Impurities:

Mg, Mn

Type Locality:

Torre di Rio - Santa Filomena area (Monte della Torre), Rio Marina, Elba Island, Livorno Province, Tuscany, Italy

Year Discovered:

1811

View mineral photos:

Ilvaite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Ilvaite is a fairly common mineral but rarely found as a faceted gem. Some of the mineral specimens are very collectable well-formed, shiny black, diamond-shaped crystals with sub-metallic luster. Gems are opaque black for collectors of the "black gem" category.

Ilvaite is found at many locations worldwide including Elba, at Rio Marina and Capo Calamita; on Mt. Mulatto, near Predazzo, Trentino-Alto Adige, Italy. Very large crystals from Seriphos, Cyclades Islands, Greece; from the Kangerdluarssuk Plateau, in the Ilímaussaq intrusion, southern Greenland; fine crystals at Dal'negorsk, Primorskiy Kray, Russia; in the USA, very fine crystals from the Laxey mine, South Mountain, Owyhee County, Idaho; and the Prince of Wales Island, Alaska.
 

  
Ilvaite gems for sale:

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