Knebelite is a manganese variety of the fayalite-tephroite series with formula (Fe, Mn)2SiO4. It forms dark green orthorhombic crystals. It is a variety of Fayalite-Tephroite Series. It is a silicate mineral, a manganese variety of fayalite that forms dark green orthorhombic crystals. It is reported from a variety of locations in Sweden as well as South Africa, Russia, British Columbia, New Hampshire, and Rhode Island. It is consisting of iron manganese silicate and occurring especially in Sweden (specific gravity 4.1).
Fig: Knebelite
Physical properties
- Cleavage: {010} Indistinct
- Color: Brown, Black, Black
- Density: 4.39
- Diaphaneity: Transparent to Translucent
- Fracture: Conchoidal – Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz)
- Habit: Granular – Generally occurs as anhedral to subhedral crystals in matrix
- Habit: Massive – Granular – Common texture observed in granite and other igneous rock
- Hardness: 6.5 – Pyrite
- Luminescence: Non-fluorescent
- Luster: Vitreous (Glassy)
- Streak: White.
