metamorphic
Quartzite with Glauconitic or Iron staining
Quartzite (SiO2 with accessory minerals)
Hardness: 7 (Mohs scale), Color: Yellowish-tan to dark grey/green mottled, Luster: Vitreous to dull, Crystal structure: Granoblastic, non-foliated, Cleavage: None/Conchoidal fracture, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Yellowish-tan to dark grey/green mottled, Luster: Vitreous to dull, Crystal structure: Granoblastic, non-foliated, Cleavage: None/Conchoidal fracture, Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure. The dark mottling suggests the presence of chlorite, glauconite, or iron oxides integrated during the recrystallization process.
Uses & applications
Primarily used as a durable aggregate in construction, railway ballast, and occasionally as a decorative landscape stone or lapidary material for tumbling.
Geological facts
Quartzite is so strong and chemically resistant that it often survives intense weathering that dissolves other rocks, which is why it is frequently found as rounded river pebbles or cobbles.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its grainy, sandpaper-like texture that doesn't rub off. It is commonly found in mountainous regions or glacial till deposits.
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