metamorphic
Quartzite
Quartzite (mostly SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, often stained yellow or pink by iron oxides; Luster: vitreous to greasy; Crystal Structure: non-foliated, granular texture; Cleavage: none (breaks with conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Luster
- vitreous to greasy
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, often stained yellow or pink by iron oxides; Luster: vitreous to greasy; Crystal Structure: non-foliated, granular texture; Cleavage: none (breaks with conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events (orogenic cycles). This specimen shows iron oxide staining common in surface weathering.
Uses & applications
Used extensively in road construction, as railway ballast, and in the manufacturing of glass and ceramics. Polished slabs are popular for countertops and decorative stones.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges because it resists erosion better than the rocks around it.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and its tendency to break across grain boundaries rather than around them, which distinguishes it from sandstone.
