metamorphic
Quartzite (Yellow/Iron-Stained)
Quartzite (SiO2 with Iron Oxide impurities)
Hardness: 7 on Mohs scale (scratches glass). Color: Creamy white with yellow/orange iron staining. Luster: Vitreous to dull. Structure: Granular/crystalline with no visible pores. Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale (scratches glass)
- Color
- Creamy white with yellow/orange iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale (scratches glass). Color: Creamy white with yellow/orange iron staining. Luster: Vitreous to dull. Structure: Granular/crystalline with no visible pores. Specific Gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure caused the original sand grains to recrystallize and fuse together. The yellow staining is due to the secondary infiltration of iron oxides (limonite/goethite) over geological time scales.
Uses & applications
Used primarily in construction as crushed stone or decorative landscaping. Higher-purity quartzite is used to produce glass, silicon metal, and ferrosilicon. Occasional use in lapidary for tumbled stones or cabochons.
Geological facts
Quartzite is so tough that it often survives the intense weathering and erosion processes that destroy other rocks. This specific specimen appears water-worn, likely found in a riverbed or glacial deposit where the friction of moving water rounded its edges into a 'river cobble'.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its break pattern (it breaks through the sand grains, not around them like sandstone). Commonly found in mountainous regions or ancient glacial drift. Tips for collectors: Check for translucency at the edges when held to high light.
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