metamorphic
Yellow Quartzite Pebble
Metamorphosed Sandstone (SiO2 with iron oxide impurities)
Hardness: 7 on Mohs scale; Color: Honey-yellow to tan; Luster: Vitreous to waxy; Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Honey-yellow to tan
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Honey-yellow to tan; Luster: Vitreous to waxy; Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. The yellow color is typically caused by the presence of iron oxides (limonite or goethite) during formation.
Uses & applications
Used as decorative landscaping stone, in construction aggregates, as a material for glass making (if high purity), and in minor lapidary work for tumbled stones.
Geological facts
Quartzite is so tough that it often outlasts the surrounding mountains, remaining as rounded river pebbles or 'erratics' long after other rocks have eroded away. It is often harder than the steel tools used to mine it.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and its sugary, granular texture when seen under magnifying lenses. Often found in riverbeds, glacial deposits, and mountain ranges globally.
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