Ilvaite is a fairly common mineral but rarely discovered as being a gem that is faceted. 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 bought 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 america, very fine crystals from the Laxey mine, South Mountain, Owyhee County, Idaho; and the Prince of Wales Island, Alaska.

Crystallography: Orthorhombic – Dipyramidal
Crystal Habit: Crystals prismatic, to 25 cm; columnar, radiating, or compact massive.
Twinning: None


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


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