metamorphic
Quartzite (Iron-stained)
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white with yellow-brown iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with yellow-brown iron staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with yellow-brown iron staining; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together. It can be found in mountain belts and Precambrian shields worldwide.
Uses & applications
Used primarily in construction as crushed stone for road grit, railroad ballast, and roofing granules. Sometimes used decoratively in landscaping or as a dimension stone for floor tiles and wall coverings.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock layers, forming prominent ridges and hills. It is harder than steel and will easily scratch glass, a key test for identification.
Field identification & locations
Identify in the field by its sugary texture and the way it fractures across grains rather than around them. Common in riverbeds and mountainous terrain. Collectors should look for unique staining or crystal pockets.
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