metamorphic
Quartzite Cobble
Meta-quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Pinkish-tan to light purple; Luster: Vitreous to dull (weathered); Crystal structure: Hexagonal (re-crystallized grains); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 – 2.65
- Hardness
- 7 on Mohs scale
- Color
- Pinkish-tan to light purple
- Luster
- Vitreous to dull (weathered)
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: Pinkish-tan to light purple; Luster: Vitreous to dull (weathered); Crystal structure: Hexagonal (re-crystallized grains); Cleavage: None (conchoidal fracture); Specific gravity: 2.6 – 2.65
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. High heat and pressure compressed the original sand grains into a dense, crystalline mass. This specimen shows 'river-worn' rounding, indicating it was transported by water long after its formation, likely dating from the Proterozoic to Paleozoic eras.
Uses & applications
Used primarily in construction for crushed stone, railway ballast, and road base. Due to its resistance to weathering, it is also used in decorative landscaping and as an abrasive.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges that create it. It is frequently mistaken for sugar-textured limestone, but unlike limestone, quartzite will not fizz in contact with vinegar or acid.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass and steel) and its granular, crystalline texture. It is commonly found in glacial till, riverbeds, and mountainous regions like the Appalachians or the Rockies.
More like this
