metamorphic
Red Quartzite
Tectonically compressed Quartz-rich rock (SiO2)
Hardness: 7 (Mohs scale), Color: Red to reddish-brown due to iron oxide impurities, Luster: Vitreous to waxy, Crystal structure: Trigonal/Hexagonal (granular), Cleavage: None, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Red to reddish-brown due to iron oxide impurities, Luster: Vitreous to waxy, Crystal structure: Trigonal/Hexagonal (granular), Cleavage: None, Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure. The red color is typically the result of hematite or other iron oxide minerals coating the original sand grains before or during metamorphism.
Uses & applications
Used in construction for road ballast, floor tiles, and countertop surfaces. Polished specimens are popular for decorative landscaping, lapidary work, and crystal collecting.
Geological facts
Quartzite is so tough that it often survives intense glacial movements and river transport where other rocks would crumble into sand. Sometimes it is confused with jasper, but quartzite has a more crystalline, granular texture when viewed closely.
Field identification & locations
Identified in the field by its extreme hardness (it will easily scratch glass or steel) and its granular, sugary texture on freshly broken surfaces. Common in mountain belts and Precambrian shields.
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