metamorphic
Orange Quartzite (River Pebble)
Quartzite (SiO2 with iron oxide impurities)
Hardness: 7 (Mohs scale); Color: Orangish-brown to honey color; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.8
- Hardness
- 7 (Mohs scale)
- Color
- Orangish-brown to honey color
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Orangish-brown to honey color; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6 - 2.8
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure reciprocal recrystallized individual sand grains into a dense, interlocking matrix of quartz crystals. The orange hue is caused by the inclusion of iron oxide (hematite or limonite) during formation or subsequent staining from groundwater.
Uses & applications
Used primarily in landscaping, construction as a base material, and crushed stone. Smooth river-worn specimens are often used in decorative water features, 'worry stones', or for lapidary tumbling for hobbyists.
Geological facts
Quartzite is harder than the sandstone from which it forms; while sandstone will break around its grains, quartzite breaks right through them. Many orange river pebbles are extremely old, having been rounded by water transport over millions of years.
Field identification & locations
Identify in the field by its inability to be scratched by a steel pocket knife and its grainy, 'sugary' texture under a magnifying lens. Commonly found in riverbeds, glacial deposits, and mountain ranges. Collectors look for uniform color and high translucency.
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