metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Off-white, yellowish-tan; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- Off-white, yellowish-tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Off-white, yellowish-tan; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.63 - 2.65
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, often during mountain-building events. This specific specimen has been further shaped and smoothed by water erosion in a river or coastal environment.
Uses & applications
Used primarily as decorative landscaping stone, in construction as aggregate, and occasionally for primitive tools or lapidary practice. High-purity quartzite is also a source of silica for glass and metal casting.
Geological facts
Quartzite is so tough that it often survives thousands of years of erosion that wears away surrounding softer rocks. It is harder than steel and will easily scratch a glass plate.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its grainy, sandpaper-like texture (if not fully water-worn). Found globally in ancient mountain belts and river beds. Tips for collectors: look for 'conchoidal' fractures that look like broken glass.
