metamorphic
Weathered quartz-rich metamorphic rock, likely quartzite
Quartzite; predominantly microcrystalline quartz (SiO₂), with minor iron-oxide staining and possible feldspar or mica
AI-generated identification · may be incorrectHardness about 7 Mohs; gray to tan with rusty-brown weathering, granular texture, and vitreous to dull luster. Quartzite typically lacks prominent cleavage and has a dense, interlocking crystalline structure.
Identified More metamorphic →
Explore Weathered quartz-rich metamorphic rock, likely quartzite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 7 Mohs; gray to tan with rusty-brown weathering, granular texture, and vitreous to dull luster. Quartzite typically lacks prominent cleavage and has a dense, interlocking crystalline structure.
Formation & geological history
Formed when quartz-rich sandstone was buried and recrystallized under heat and pressure, commonly during regional mountain-building; its exact geological age cannot be determined from the photograph. The brown areas likely reflect oxidation of iron-bearing impurities.
Uses & applications
Used as crushed stone, road aggregate, riprap, building stone, and occasionally countertops or decorative material. Ordinary field specimens generally have little commercial value.
Geological facts
A diagnostic feature is that quartzite breaks through quartz grains rather than around them, unlike weakly cemented sandstone. The specimen may alternatively be quartz-rich gneiss or heavily cemented sandstone, which requires a fresh surface or tests for certainty.
Field identification & locations
Common in metamorphic mountain belts worldwide, including the Appalachian Mountains, Rocky Mountains, and Precambrian shields. Look for resistance to scratching by steel and inability to scratch glass reliably only if quartz is abundant; a streak test and fresh fracture help distinguish it from sandstone.
More like this
