metamorphic
Quartzite and Milky Quartz River Pebbles
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: white, grey with black veins, and tan/brown; Luster: vitreous to waxy; Crystal structure: hexagonal/trigonal; Cleavage: none (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- white, grey with black veins, and tan/brown
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: white, grey with black veins, and tan/brown; Luster: vitreous to waxy; Crystal structure: hexagonal/trigonal; Cleavage: none (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. These specific specimens are water-worn river pebbles, smoothed over long periods of time in high-energy fluvial environments.
Uses & applications
Commonly used in landscaping, as decorative aggregate, in construction, and occasionally for lapidary work or aquarium decor.
Geological facts
The dark banding in the grey pebble is likely due to organic carbon or iron oxide impurities within the quartz matrix. Quartz is one of the most abundant and durable minerals on Earth's crust.
Field identification & locations
Identify by their smooth, rounded shapes indicating water transport, and their high hardness—they will easily scratch glass. Commonly found in riverbeds, glacial tills, and coastal beaches.
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