metamorphic
Quartzite (Yellow/Orange variety)
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Yellow, orange, tan (due to iron inclusions); Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Yellow, orange, tan (due to iron inclusions)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellow, orange, tan (due to iron inclusions); Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone (sedimentary rock) under intense heat and pressure. The original sand grains recrystallize and fuse together into a dense, crystalline rock.
Uses & applications
Used as decorative stone in landscaping, crushed for road construction, and occasionally for making arrowheads or primitive tools due to its hardness and durability.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges of mountain ranges. It is harder than the steel of a knife, which is a key way to distinguish it from softer rocks like marble or calcite.
Field identification & locations
Identify in the field by its grainy, 'sugary' texture and high hardness (it will easily scratch glass). Common in metamorphic belts and as stream-worn river cobbles. Look for the way the rock breaks through the sand grains rather than around them.
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