metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: White to light tan/yellow, Luster: Vitreous to dull, Crystal structure: Trigonal (granoblastic texture), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: White to light tan/yellow, Luster: Vitreous to dull, Crystal structure: Trigonal (granoblastic texture), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. It can date back to various geological eras depending on location.
Uses & applications
Used in construction as crushed stone for road beds, in glass making (if high purity), and in manufacturing refractory bricks. High-quality slabs are used for countertops and flooring.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, forming prominent ridges and hills. It is harder than steel and can easily scratch glass.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and its grainy, crystalline appearance. It lacks the layered look of gneiss or the fizzing reaction of marble to acid. Found abundantly in mountain ranges.
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