metamorphic
Quartzite (River Pebble)
Metamorphosed Quartz Sandstone (primarily SiO2)
Hardness: 7 (Mohs scale), Color: White to light grey, Luster: Vitreous to waxy, Crystal structure: Hexagonal/Trigonal (microcrystalline), Cleavage: None, Specific Gravity: 2.63–2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: White to light grey, Luster: Vitreous to waxy, Crystal structure: Hexagonal/Trigonal (microcrystalline), Cleavage: None, Specific Gravity: 2.63–2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, which causes the sand grains to recrystallize into an interlocking mosaic. This specimen has been further shaped and smoothed by fluvial (river) erosion.
Uses & applications
Commonly used in construction as crushed stone or road ballast, as a decorative stone in landscaping, and in the manufacturing of glass and ceramics.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, forming ridges and resistant peaks. It is famous for its durability, which is significantly higher than marble.
Field identification & locations
Identify in the field by its hardness (it should easily scratch glass) and its sugary, granular look on fresh breaks. This specific specimen is found in riverbeds and on beaches worldwide.
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