Ilvaite
Chemical Formula	Ca(Fe2+)2Fe3+[O|OH|Si2O7]
Species	Silicates
Crystal System	Orthorhombic
Mohs Scale	5-6
Specific Gravity	3.8-4.1
Color	Iron-black, dark grayish black
Streak	black
Luster	Sub-Metallic
Refractive Index	n = 1.727 n = 1.870 n = 1.883
Diaphaneity	Opaque
Cleavage	Distinct/GoodDistinct on
Fracture	Irregular/Uneven
Crystal Habit：Prismatic, columnar, radiating, compact massive,
Geological Setting：Contact metasomatic rocks and iron deposits.