metamorphic
Yellow Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Yellow to tan from iron oxide staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Yellow to tan from iron oxide staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Yellow to tan from iron oxide staining; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize the quartz grains into a dense, interlocking mosaic of crystals. Found in mountain belts like the Appalachians or Alps, dating from Precambrian to Paleozoic eras.
Uses & applications
Used as crushed stone for road construction and railway ballast. High-purity quartzite is used to produce ferrosilicon and industrial silica. Water-worn pebbles like this are popular for landscaping and decorative gardens.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it forms within, ending up as resilient river or beach gravel like this specimen. It can be distinguished from sandstone because it breaks through the grains rather than around them.
Field identification & locations
Identify in the field by its inability to be scratched by a steel pocket knife and its characteristic 'sugary' texture on fresh breaks. This specimen shows significant rounding from water transport. Common in river beds and glacial deposits.
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