Limonite with Goethite
Limonite (mineraloid) containing Goethite [α-Fe3+O(OH)] · Mineral Specimen and Geological Ore
Crystal System
Amorphous or Monoclinic/Orthorhombic (if crystalline); typically massive, botryoidal, or earthy habit
Mineral Group
Oxides and Hydroxides
Chemical Formula
FeO(OH)·nH2O with variable manganese oxides and silica
Formation Process
Secondary formation via chemical weathering of iron-rich minerals such as pyrite, magnetite, and siderite in the oxidation zone of ore deposits
About This Crystal
Massive and earthy appearance with a distinctive yellow to brownish-orange 'ochre' body. Displays a dull to sub-metallic luster on fresh surfaces, often showing iridescent tarnish or 'oil-on-water' blue-purple patinas on metallic lusters
Physical Characteristics
Yellow-brown streak; no cleavage; uneven or conchoidal fracture; specific gravity 2.7 to 4.3; typically non-fluorescent; opaque
Optical Properties
Isotropic to anisotropic depending on crystallinity; refractive index approx. 2.0 to 2.4; lacks transparency/fire; tarnish may produce thin-film interference colors
Hardness & Durability
Origin Region
Worldwide, notably Minas Gerais (Brazil), Germany, and various iron mining districts in the United States and Australia
Hardness & Durability
Mohs hardness 4 to 5.5; brittle toughness; unstable in acidic environments and becomes dehydrated upon heating
Care & Maintenance
Clean with a soft brush only; avoid water and ultrasonic cleaning which can degrade earthy surfaces; keep away from harsh chemicals and high heat
Rarity & Value
Common; primarily valued as iron ore or as a pigment; iridescent specimens hold higher value for collectors
Special Characteristics
Often presents iridescent 'rainbow' coatings due to thin film oxidation; can form pseudomorphs after crystals like pyrite
Lore & History
Used as the pigment 'Yellow Ochre' in cave paintings and ancient cosmetics; historically recognized as a grounder in traditional lore, associated with the Root and Sacral Chakras