metamorphic
River Cobble (Quartzite)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or white with reddish-brown staining; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Specific gravity: approx. 2.6
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or white with reddish-brown staining
- Luster
- Vitreous to dull
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or white with reddish-brown staining; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Specific gravity: approx. 2.6
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been rounded and smoothed by water transport in a river or fluvial environment over thousands of years.
Uses & applications
Commonly used in construction as railway ballast, crushed stone for road bases, and decorative landscaping. High-purity quartzite is used to produce silica sand for glassmaking.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges. It is tougher than the parent sandstone from which it originated.
Field identification & locations
Identify by its extreme hardness (it will scratch glass) and lack of reaction to acid. The rounded shape indicates it was likely found in a creek bed, river, or glacial deposit. Commonly found worldwide in metamorphic terrains.
More like this
