metamorphic
Quartzite (with Iron Staining)
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale); Color: Pale yellow to tan with iron-oxide staining; Luster: Vitreous to waxy; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture)
- Hardness
- 7 (Mohs scale)
- Color
- Pale yellow to tan with iron-oxide staining
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Pale yellow to tan with iron-oxide staining; Luster: Vitreous to waxy; Structure: Granular, non-foliated; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically during regional metamorphism at convergent plate boundaries. The yellow hue comes from traces of limonite or goethite minerals.
Uses & applications
Used extensively in road construction as aggregate, as a decorative stone in landscaping, and sometimes in the manufacturing of glass or ceramics due to high silica content.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges, outlasting softer rocks around it. It is harder than a steel knife blade.
Field identification & locations
Identified in the field by its grainy, sugary appearance and its ability to scratch glass. It will not fizz with acid, distinguishing it from marble. Common in metamorphic belts worldwide.
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