metamorphic
Quartzite (Rounded Pebble)
Quartzite (predominantly SiO2)
Hardness: 7 (Mohs scale); Color: Translucent tan to creamy white; Luster: Vitreous to waxy; Crystal structure: Hexagonal (as individual grains); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Translucent tan to creamy white
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Translucent tan to creamy white; Luster: Vitreous to waxy; Crystal structure: Hexagonal (as individual grains); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the original sand grains to recrystallize and fuse together, losing their original sedimentary texture. This specimen appears to have been rounded by water transport (alluvial processes).
Uses & applications
Commonly used in construction as crushed stone or gravel, in industrial glass making (if high purity), and as an ornamental stone in landscaping or lapidary work.
Geological facts
Quartzite is so strong that when it breaks, it fractures through the quartz grains rather than along the boundaries between them, unlike its parent stone, sandstone. It is extremely resistant to chemical weathering.
Field identification & locations
Identify in the field by its hardness (will scratch glass and steel) and its grainy but fused texture. It is ubiquitous in riverbeds, glaciated areas, and mountain ranges worldwide. Collectors look for unique colors or high translucence.
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