metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: light gray, tan, or white with translucent patches; Luster: Vitreous to dull; Structure: Non-foliated, granular; Specific Gravity: 2.6-2.7. It is extremely durable and lacks a sugary texture common in sandstone.
- Hardness
- 7 on Mohs scale
- Color
- light gray, tan, or white with translucent patches
- Luster
- Vitreous to dull
Identified More metamorphic →
Explore Quartzite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: light gray, tan, or white with translucent patches; Luster: Vitreous to dull; Structure: Non-foliated, granular; Specific Gravity: 2.6-2.7. It is extremely durable and lacks a sugary texture common in sandstone.
Formation & geological history
Quartzite is formed when quartz-rich sandstone is subjected to high heat and pressure during regional metamorphism. The individual quartz grains recrystallize and interlock, forming a very strong rock. They are commonly found in folded mountain belts and ancient cratons.
Uses & applications
Used as decorative stone in construction, road ballast, railway ballast, and occasionally as a source of silica for glass manufacturing or as a refractory material. Small stream-worn pebbles are often used in landscaping.
Geological facts
Quartzite is so hard that it can scratch a knife blade. In ancient times, it was sometimes used to create stone tools when flint was unavailable. It is more resistant to weathering than the surrounding rock, often forming the peaks of ridges and mountains.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. It often appears 'glassy' or slightly translucent on fresh breaks. Found globally in areas with metamorphic history.
More like this
