metamorphic
Quartzite with Sandstone/Iron staining
Metamorphic Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: White, cream, and yellow/tan; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- White, cream, and yellow/tan
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: White, cream, and yellow/tan; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. The yellow/tan layering is caused by iron-oxide staining or residual sedimentary bedding from the parent sandstone.
Uses & applications
Used primarily as decorative river stone, in landscaping, as a lapidary material for tumbling, and historically as a source for high-purity silica in industrial manufacturing.
Geological facts
Quartzite is so hard and chemically resistant that it often survives as rounded pebbles in riverbeds and beaches long after other rocks have eroded away. The distinct banding in this specimen represents the original sedimentary layers of the sand it once was.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass) and its sugary/crystalline texture on broken surfaces. It is commonly found in glacial till, riverbeds, and mountainous regions worldwide.
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