metamorphic
Quartzite (River-worn Shiner)
Quartzite (Formula: SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, and translucent grey with iron staining; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, and translucent grey with iron staining
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, and translucent grey with iron staining; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize the sand grains into a dense, interlocking matrix. This specific specimen shows alluvial weathering, indicating it was transported and rounded by water action over thousands of years.
Uses & applications
Commonly used as high-quality construction aggregate, railway ballast, and in the manufacturing of glass or ceramics. Polished versions are often used for decorative 'river stones' in landscaping.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges that create it. This specimen's rounded shape is a result of millions of impacts against other rocks in a riverbed, which eventually smooths out the jagged edges of the original metamorphic block.
Field identification & locations
Identify in the field by checking for its ability to scratch glass and its granular, sugary texture under a hand lens. It lacks the banding of agate. It is commonly found in ancient mountain belts and modern river drainage basins.
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