Limonite and Calcite on Matrix
Goethite/Limonite with Calcite (Calcium Carbonate) · Mineral Specimen / Decorative Stone
Crystal System
Amorphous or Orthorhombic (Goethite), Trigonal (Calcite); Habit is massive, earthy, and crust-like
Mineral Group
Oxides / Carbonates
Chemical Formula
FeO(OH)·nH2O (Limonite) and CaCO3 (Calcite)
Formation Process
Secondary formation via weathering and oxidation of iron-rich minerals (Sedimentary/Hydrothermal oxidation)
About This Crystal
The specimen shows an earthy, matte brown-to-yellowish Limonite matrix with small, white, crust-like or druzy patches of Calcite. Overall opaque with a dull to earthy luster on the matrix and vitreous luster on the white crystalline inclusions.
Physical Characteristics
Color: Brown, ochre, white. Streak: Yellowish-brown (Limonite), White (Calcite). Cleavage: None for Limonite; Rhombohedral for Calcite. Fracture: Uneven/Earthy. Fluorescence: Calcite may glow red or orange under UV.
Optical Properties
Opaque (matrix) to translucent (spots); No observable pleochroism or dispersion in this massive form.
Hardness & Durability
Origin Region
Worldwide; common in iron-rich oxidation zones of ore deposits (e.g., Minas Gerais, Brazil; Arizona, USA; Morocco)
Hardness & Durability
Mohs 4 - 5.5 for Limonite; 3 for Calcite. Very brittle and susceptible to scratching.
Care & Maintenance
Keep dry; sensitive to acids (Calcite will effervesce). Clean with a soft, dry brush. Do not use ultrasonic cleaners or harsh chemicals.
Rarity & Value
Common; very low market value. Primarily valued as an educational or geological specimen rather than a gemstone.
Special Characteristics
Porous texture; possible pseudomorphism where iron oxides replace previous mineral shapes.
Lore & History
Limonite was historically used as a primary iron ore and a source of ochre pigment for cave paintings. Metaphysically, it is associated with grounding and stability.