metamorphic
Yellow Quartzite (Iron-Stained Quartzite)
Quartzite (SiO2 with Fe2O3 trace impurities)
Hardness: 7 on Mohs scale; Color: Yellow, honey, or mustard yellow; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- Yellow, honey, or mustard yellow
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellow, honey, or mustard yellow; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone. Intense heat and pressure cause the quartz grains to recrystallize and fuse together. The yellow color is typically due to iron oxide staining during or after formation.
Uses & applications
Used in landscaping, road construction, as an architectural decorative stone, and sometimes for lapidary work like cabochons or tumbled stones.
Geological facts
Quartzite is so hard that it will scratch glass and steel. Unlike sandstone, when quartzite breaks, the fracture passes through the quartz grains rather than around them because the grains are so tightly fused.
Field identification & locations
Identify by its extreme hardness and grainy yet fused texture. It is commonly found in mountain ranges or areas of continental collision. In the field, look for a rock that cannot be scratched by a steel knife and has a slightly sugary appearance on fresh surfaces.
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