metamorphic
Quartzite pebble
Quartzite (SiO2) with iron oxide staining
Hardness: 7 (Mohs scale), Color: White with brownish-tan bands/staining, Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.6-2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: White with brownish-tan bands/staining, Luster: Vitreous to dull, Crystal structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.6-2.65
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been smoothed and rounded by water erosion (fluvial or beach action) and contains iron-rich mineral staining or layering.
Uses & applications
Commonly used in landscaping, as a construction aggregate, and as a decorative garden stone. Pure quartzite is also used for making glass and in metal smelting.
Geological facts
Quartzite is so hard and dense that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike sandstone. The brown coloring is usually due to the presence of hematite or limonite.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sugary texture. Commonly found in riverbeds, glacial tills, and ancient mountain belts. Look for a translucent quality in the white sections.
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