metamorphic
Quartzite (Gold-Yellow variety)
Quartzite (Silicon Dioxide, SiO2)
Hardness: 7 (Mohs scale); Color: Pale yellow to golden brown; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline aggregate); Cleavage: None; Specific gravity: 2.6 - 2.7
- Hardness
- 7 (Mohs scale)
- Color
- Pale yellow to golden brown
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Pale yellow to golden brown; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline aggregate); Cleavage: None; Specific gravity: 2.6 - 2.7
Formation & geological history
Formed through the heating and pressure (metamorphism) of quartz-rich sandstone. It typically originates in convergent plate boundaries where intense pressure transforms the original sand grains into a recrystallized interlocking mosaic of quartz.
Uses & applications
Used in construction as crushed stone or decorative aggregates. Larger high-purity pieces are used in the manufacturing of silicon for electronics or as a source of silica glass.
Geological facts
Quartzite is so tough that it often breaks through the constituent sand grains rather than around them, which distinguishes it from sandstone. This specimen likely owes its yellow hue to iron oxide staining (limonite).
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife (unlike calcite or gypsum) and its grainy, sugary texture. Commonly found in mountainous regions or as river-tumbled pebbles.
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