metamorphic
Quartzite River Rock
Metamorphic Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: light grey to bluish-grey with white speckling, Luster: dull to vitreous, Structure: granular and non-foliated, Cleavage: none (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: light grey to bluish-grey with white speckling, Luster: dull to vitreous, Structure: granular and non-foliated, Cleavage: none (conchoidal fracture)
Formation & geological history
Formed through the regional metamorphism of quartz sandstone. The original sand grains are recrystallized and fused together by heat and pressure, often found in ancient belt terrains and subsequently eroded into river beds.
Uses & applications
Commonly used as decorative landscaping stone, in construction as road ballast, and as a durable material for stone tools in prehistoric times.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks; when struck, it breaks across the quartz grains rather than around them, which distinguishes it from sandstone.
Field identification & locations
Identify by its extreme hardness (scratches glass) and sugary, crystalline appearance on a fresh surface. Found globally in riverbeds and mountainous regions. Collectors look for unique shapes polished naturally by water.
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