metamorphic
Quartzite
Quartzite (chiefly SiO2)
Hardness: 7 on Mohs scale; Color: typically white, gray, or pinkish; Luster: vitreous (glassy) to dull; Crystal structure: hexagonal (within grains); Cleavage: none; Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- typically white, gray, or pinkish
- Luster
- vitreous (glassy) to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: typically white, gray, or pinkish; Luster: vitreous (glassy) to dull; Crystal structure: hexagonal (within grains); Cleavage: none; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartzose sandstone. Intense heat and pressure cause the quartz grains to recrystallize and fuse together, losing the original sedimentary texture.
Uses & applications
Used in construction as crushed stone or decorative facing, in the manufacturing of glass and ceramics, and as a durable material for kitchen countertops.
Geological facts
Quartzite is so hard that it will scratch glass and even some steel tools. It is also highly resistant to chemical weathering, which is why it often forms prominent ridges on mountain ranges.
Field identification & locations
Identify in the field by its extreme hardness and tendency to break across the quartz grains rather than around them (unlike sandstone). Commonly found in ancient mountain belts such as the Appalachians or the Alps.
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