Limonite with Mica
Goethite/Hematite mixture (Limonite) with Muscovite · Mineral Specimen / Industrial Ore
Crystal System
Amorphous to Orthorhombic (Limonite); Monoclinic (Mica). Habit is typically massive, earthy, or micaceous/flaky.
Mineral Group
Oxides/Hydroxides (Limonite) and Silicates (Phyllosilicates - Mica)
Chemical Formula
FeO(OH)·nH2O (Limonite) + KAl2(AlSi3O10)(OH)2 (Muscovite)
Formation Process
Secondary formation via weathering and oxidation of iron-bearing minerals; mica is often a metamorphic or igneous primary constituent of the host rock.
About This Crystal
The specimen shows an earthy, yellowish-orange to rusty brown mass of limonite embedded in or coating a dark, greyish-brown host rock. Small, reflective silvery-white flakes of mica (likely muscovite) provide a sparkling luster against the dull, opaque background.
Physical Characteristics
Color: Yellow-brown to dark gray. Streak: Yellowish-brown. Luster: Earthy to metallic (on mica flakes). Cleavage: Perfect basal on mica, none on limonite. Specific Gravity: 2.7 to 4.3.
Optical Properties
Limonite is opaque; mica flakes are transparent to translucent with pearly luster. No significant birefringence or pleochroism visible in this hand specimen.
Hardness & Durability
Origin Region
Global; common in oxidized zones of iron-rich ore deposits and sedimentary ironstones.
Hardness & Durability
Mohs Hardness: 4 - 5.5 for limonite, 2 - 2.5 for mica. Brittle and prone to crumbling; not suitable for jewelry.
Care & Maintenance
Keep dry as moisture can alter the hydration state of limonite. Clean only with a soft, dry brush; water or ultrasonics may cause the earthy material to disintegrate.
Rarity & Value
Common. It is valued primarily as an iron ore or a geological teaching specimen. Very low market value for raw individual specimens.
Special Characteristics
The specimen exhibits a sparkling effect due to the mica flakes (schistose appearance) and contains iron hydroxides that act as natural pigments.
Lore & History
Historically used as 'ochre' for cave paintings and pigments. In lore, it is believed to provide grounding and stability; mica is traditionally associated with mental clarity.