metamorphic
Quartzite (Iron-stained River Rock)
Metamorphic Rock consisting primarily of Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, orange-brown, and white with iron oxide staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); High durability.
- Hardness
- 7 on Mohs scale
- Color
- Tan, orange-brown, and white with iron oxide staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, orange-brown, and white with iron oxide staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); High durability.
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing quartz grains to recrystallize into a dense network. This specific specimen has been further shaped by fluvial (river) erosion and stained by iron-rich water.
Uses & applications
Commonly used in landscaping, as a base for road construction, in high-silica glass manufacturing, and as decorative river stones.
Geological facts
Quartzite is so tough that it often survives intense weathering that destroys other rocks. The orange and brown tints on the surface are 'limonite' or iron oxide rinds formed by prolonged exposure to oxygen and water.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its sugary, crystalline texture when broken. Found in riverbeds and mountainous regions globally. Often mistaken for chert, but has a more granular appearance.
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