metamorphic
Quartzite River Rock
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or white with brown spotting; Luster: Dull to vitreous; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or white with brown spotting
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or white with brown spotting; Luster: Dull to vitreous; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This specific specimen has been further shaped by fluvial (river) erosion, which smoothed its edges over centuries.
Uses & applications
Used primarily in construction as crushed stone or decorative landscaping. High-purity quartzite is used in glassmaking and electronics. Tumbled river rocks are popular in home decor.
Geological facts
Quartzite is so hard that it can scratch steel and even glass. It is often more resistant to weathering than the surrounding rock, often forming the summits of ridges and mountains.
Field identification & locations
Identify in the field by its extreme hardness, grainy texture that looks like sandstone but won't rub off, and its characteristic sparkle on fresh surfaces. Found globally in riverbeds and ancient metamorphic belts.
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