metamorphic

Ferruginous Quartzite (Chert)

Quartzite with Iron inclusions (SiO2 + Fe2O3)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale. Color: Reddish-brown, tan, orange-brown (due to iron oxidation). Luster: Dull to waxy. Crystal structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture).

Hardness: 7 on Mohs scale
Color: Reddish-brown, tan, orange-brown (due to iron oxidation)
Luster: Dull to waxy

Identified April 12, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed from the metamorphism of quartz-rich sandstone or the silification of sedimentary deposits. The reddish-brown color comes from iron oxides staining the quartz during or after formation. Most specimens date from the Proterozoic to Paleozoic eras.

Uses & applications

Used primarily in landscaping, road construction as aggregate, and occasionally by flint-knappers for making stone tools. It is also collected by hobbyists for tumbling.

Geological facts

Quartzite is so hard that it will scratch glass and steel. This specific iron-rich variety is often mistaken for petrified wood or common jasper because of its earthy color palette.

Field identification & locations

Identify in the field by its extreme hardness, lack of horizontal grain (unlike sandstone), and its rough, grainy surface texture that still shows a spark when struck with steel. Commonly found in riverbeds and glacial till.