metamorphic
Yellow Quartzite
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Yellow, tan, or golden-brown due to iron oxide impurities; Luster: Vitreous to dull; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Yellow, tan, or golden-brown due to iron oxide impurities
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Yellow, tan, or golden-brown due to iron oxide impurities; Luster: Vitreous to dull; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the original sand grains to recrystallize into a dense, interlocking mosaic of quartz crystals. Can range from Precambrian to Cenozoic in age depending on the location.
Uses & applications
Used as a decorative stone in landscaping, a crushed stone in road construction, and occasionally in glassmaking or as a semi-precious stone for lapidary work and beads.
Geological facts
Quartzite is so tough that it often forms the caps of mountains because it resists weathering better than surrounding rocks. It is often confused with marble but can be distinguished by its hardness (quartzite scratches glass, marble does not).
Field identification & locations
Identify in the field by its sugary texture and extreme hardness. It will scratch steel and glass. Found globally in mountainous regions or ancient shield areas like the Appalachians, the Scottish Highlands, or the Brazilian Highlands.
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