mineral
Ferruginous Quartz
Silicon Dioxide (SiO2) with iron oxide inclusions (Limonite/Hematite)
Hardness: 7 (Mohs scale); Color: White to milky with reddish-brown staining; Luster: Vitreous to dull; Crystal structure: Trigonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- White to milky with reddish-brown staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: White to milky with reddish-brown staining; Luster: Vitreous to dull; Crystal structure: Trigonal; Cleavage: None/Conchoidal fracture; Specific gravity: 2.65.
Formation & geological history
Formed through hydrothermal processes where silica-rich fluids crystallize in veins or cavities. The reddish-brown staining is caused by secondary iron oxide minerals (limonite or hematite) leaching into cracks and surfaces. Common in the Schwaner Mountains and varied geological settings of Kalimantan.
Uses & applications
Used primarily for industrial glass making, filtration, and as a decorative mineral specimen. In jewelry, clear varieties are faceted, but this rough specimen is mostly for geological study or collection.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. Specimens found in tropical regions like Borneo often exhibit heavy staining due to intense chemical weathering (lateritization) of surrounding soils.
Field identification & locations
Identify in the field by its ability to scratch glass and its lack of cleavage. In Central Kalimantan (0.9°S, 113.9°E), it is often found in riverbeds or near igneous outcrops associated with the Mueller or Schwaner ranges.
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