metamorphic
Quartzite (Iron-stained)
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale. Color: Tan, golden-yellow to brownish (due to iron oxide staining). Luster: Vitreous (glassy) to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.6 – 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Tan, golden-yellow to brownish (due to iron oxide staining)
- Luster
- Vitreous (glassy) to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan, golden-yellow to brownish (due to iron oxide staining). Luster: Vitreous (glassy) to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.6 – 2.65.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. High heat and pressure cause the original quartz grains to recrystallize and fuse together. It can range from Precambrian to Cenozoic in age depending on the local geology.
Uses & applications
Used extensively in construction as road ballast, gravel, and dimension stone for flooring or walls. Highly durable, it is also used as a source of silica in glass manufacturing and as an ornamental stone in landscaping.
Geological facts
Quartzite is so tough that it often breaks through the constituent quartz grains rather than along their boundaries, unlike its parent rock, sandstone. The yellowish-orange hue in this specimen is caused by the infiltration of hematite or limonite into the microscopic pores.
Field identification & locations
Identify in the field by its superior hardness (it will easily scratch glass and steel) and its grainy, sugary texture. It is commonly found in mountainous regions or ancient cratons worldwide, especially in the Appalachian or Rocky Mountains in North America.
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