metamorphic
Quartzite pebble with Mafic inclusions
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: Tan to off-white with dark grey/black inclusions. Luster: Vitreous to dull. Granular texture, extremely durable, and resistant to chemical weathering.
- Hardness
- 7 on Mohs scale
- Color
- Tan to off-white with dark grey/black inclusions
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale. Color: Tan to off-white with dark grey/black inclusions. Luster: Vitreous to dull. Granular texture, extremely durable, and resistant to chemical weathering.
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone subjected to high heat and pressure, causing recrystallization. The dark patches are likely trapped mafic minerals or rock fragments (xenoliths) that existed within the original sedimentary matrix.
Uses & applications
Commonly used as construction aggregate, decorative landscaping stone, and in the manufacturing of glass and ceramics when high purity is present. This specific specimen serves as a common geological collector's item or a 'pocket stone'.
Geological facts
Quartzite is so tough that it often survives intense glacial transport and river erosion, which is why it is frequently found as rounded river pebbles like this one. It is often harder than the steel of a pocket knife.
Field identification & locations
Identify in the field by its ability to scratch glass and its lack of reaction to acid. Often found in riverbeds, glacial tills, and mountainous regions where ancient sedimentary basins were uplifted.
