metamorphic
Quartzite pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: reddish-brown due to iron oxide staining, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture, SG: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: reddish-brown due to iron oxide staining, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture, SG: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure causes recrystallization of the quartz grains. This specific specimen shows significant rounding from alluvial or river transport.
Uses & applications
Commonly used in construction as crushed stone for road beds or surfaces. Tumbled specimens are used in landscaping and as decorative 'river stones'.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them, unlike its precursor sandstone. This specimen's red hue is likely due to 'desert varnish' or iron staining from its environment.
Field identification & locations
Identify in the field by its hardness (will easily scratch glass) and lack of reaction to acid. Often found in riverbeds, glacial deposits, or mountainous regions of metamorphic outcrop.
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