metamorphic
Yellow Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Yellow to tan; Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal) in microcrystalline form; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Yellow to tan
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellow to tan; Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal) in microcrystalline form; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, causing sand grains to recrystallize into a dense network. This specific specimen has been rounded and smoothed by water erosion in a river or beach environment.
Uses & applications
Used primarily as decorative stone in landscaping, as aggregate in construction, and occasionally for lapidary work like rock tumbling.
Geological facts
Quartzite is so tough that it often survives transport over hundreds of miles in river systems; it is harder and more durable than the parent sandstone from which it originated.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and its sugary, crystalline texture when broken. Commonly found in glacial till, riverbeds, and mountainous regions.
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