metamorphic
Quartzite (or Iron-Stained Quartz Pebble)
Silicon Dioxide (SiO2) with Ferric Oxide inclusions
Hardness: 7 (Mohs scale), Color: Orange-pink to tan due to iron oxidation, Luster: Vitreous to waxy, Crystal structure: Hexagonal/Trigonal (microcrystalline), Specific gravity: 2.6 – 2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Orange-pink to tan due to iron oxidation, Luster: Vitreous to waxy, Crystal structure: Hexagonal/Trigonal (microcrystalline), Specific gravity: 2.6 – 2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing recrystallization. This specific piece has been water-worn into a river pebble shape, likely over thousands of years.
Uses & applications
Used in landscaping, road construction, and as an industrial abrasive. Polished specimens may be used in decorative gravel or as pocket stones for collectors.
Geological facts
Quartzite is so hard that it can scratch steel and glass. The orange hue is caused by tiny amounts of iron hematite or limonite staining the pores between the quartz grains.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel knife) and its grainy, sugary texture under a hand lens. Commonly found in riverbeds, glacial deposits, and sedimentary basins worldwide.
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