metamorphic
Red Quartzite / Ferruginous Quartzite
Quartzite (SiO2 with Iron Oxide impurities)
Hardness: 7 on Mohs scale; Color: Reddish-brown to orange-tan; Luster: Vitreous to dull/waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown to orange-tan
- Luster
- Vitreous to dull/waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown to orange-tan; Luster: Vitreous to dull/waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. The red coloring is caused by the inclusion of iron oxide (hematite) during or after deposition.
Uses & applications
Used in landscaping, construction (as crushed stone or decorative facing), and sometimes as a minor gemstone or decorative tumble-stone.
Geological facts
Quartzite is so hard that it can scratch glass and steel. It is frequently more durable than the parent sandstone from which it originated, often forming resistant ridges in mountain ranges.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a knife) and grainy, crystalline texture that breaks through the grains rather than around them. Common in precambrian shields and eroded mountain belts.
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