metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: typically white to gray, pinkish/reddish due to iron oxide; Luster: vitreous to dull; Crystal structure: granular, non-foliated; Cleavage: none (fractures across grains); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white to gray, pinkish/reddish due to iron oxide
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white to gray, pinkish/reddish due to iron oxide; Luster: vitreous to dull; Crystal structure: granular, non-foliated; Cleavage: none (fractures across grains); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize and fuse together. Often associated with Precambrian or Paleozoic tectonic events.
Uses & applications
Used in construction as crushed stone for road gravel and railway ballast, as a dimension stone for floor tile and wall coverings, and high-purity quartzite is used to produce silica sand for glass manufacturing.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock in weathering processes, forming prominent ridges and hills. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its sugary texture and the way it breaks through sand grains rather than around them. Commonly found in mountainous regions or glacial till deposits. Collectors look for pieces with interesting iron staining or banding.
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