metamorphic
Quartzite (Iron-stained)
Quartzite (SiO2 with Fe2O3 inclusions)
Hardness: 7 on Mohs scale. Color: Buff, yellowish-tan to reddish-brown due to iron oxide staining. Luster: Vitreous to dull/sugary. Crystal Structure: Hexagonal (microcrystalline framework). Cleavage: None (conchoidal to uneven fracture). Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to dull/sugary
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Physical properties
Hardness: 7 on Mohs scale. Color: Buff, yellowish-tan to reddish-brown due to iron oxide staining. Luster: Vitreous to dull/sugary. Crystal Structure: Hexagonal (microcrystalline framework). Cleavage: None (conchoidal to uneven fracture). Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under intense heat and pressure, causing original quartz grains to recrystallize into a interlocking mosaic of quartz crystals. Iron oxides permeate the rock during or post-metamorphism, giving it a yellow-reddish hue.
Uses & applications
Used extensively in construction as crushed stone, road ballast, decorative landscaping stone, and occasionally for building facings or stone walls due to its extreme durability.
Geological facts
Unlike sandstone, which breaks around individual quartz grains, quartzite breaks directly through the quartz grains because of its tightly interlocking crystal structure. This makes it far harder and more resistant to weathering than its parent rock.
Field identification & locations
Identify in the field by its extreme hardness (scratches glass easily), sugary crystalline texture, and resistance to acid. Commonly found in mountainous regions, ancient metamorphic terrains, and river deposits across North America, Europe, and Asia.
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