metamorphic
Yellow Quartzite (Onyx Pebble)
Silicon Dioxide (SiO2) - Quartzite
Hardness: 7 on Mohs scale; Color: Pale yellow to honey-orange; Luster: Vitreous to waxy; Structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 – 2.7.
- Hardness
- 7 on Mohs scale
- Color
- Pale yellow to honey-orange
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Pale yellow to honey-orange; Luster: Vitreous to waxy; Structure: Granular/Microcrystalline; 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. This specific rounded specimen is a river-tumbled pebble, likely dating from the Paleozoic or Mesozoic eras depending on the local bedrock source.
Uses & applications
Used primarily in decorative landscaping, aquarium stones, and as 'pocket stones' for metaphysical collectors. In bulk, quartzite is used for road ballast and industrial glass manufacture.
Geological facts
Quartzite is so durable that it often survives multiple cycles of erosion, remaining as pebbles long after the surrounding softer rocks have turned to soil. This specimen's rounded shape is a result of fluvial (river) or glacial transport.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its lack of reaction to acid (unlike calcite/limestone). Common in riverbeds, glaciated regions, and ancient sedimentary basins.
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