metamorphic
Yellow Quartzite (River Stone)
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: Yellow to tan with gray undertones, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Yellow to tan with gray undertones, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure. This specific specimen has been further shaped by fluvial erosion (river action), becoming a smooth pebble.
Uses & applications
Used as decorative gravel in landscaping, as an abrasive in construction, and occasionally for lapidary work or as worry stones.
Geological facts
Quartzite is harder and more durable than the parent sandstone it comes from. It was sometimes used by prehistoric humans to make stone tools when flint and chert were unavailable.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sugary, crystalline texture when broken. Commonly found in riverbeds, glacial deposits, and sedimentary basins worldwide.
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