metamorphic
Ferruginous Quartzite (Red Chert/Jasper-like)
Metamorphosed Quartzite with Hematite inclusions (SiO2 + Fe2O3)
Hardness: 7 (Mohs scale); Color: Reddish-brown, earthy orange; Luster: Dull to waxy; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Reddish-brown, earthy orange
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Reddish-brown, earthy orange; Luster: Dull to waxy; Crystal Structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone. The red coloration is due to the presence of iron oxides (hematite) during the deposition or metamorphic process. It is often found in Precambrian shield regions.
Uses & applications
Primary uses include decorative landscaping stone, railroad ballast, and construction aggregate. High-quality red specimens are sometimes used as lapidary material for cabochons or tumbled stones.
Geological facts
Quartzite is so durable that it often survives intense weathering that destroys other rocks, leading to 'quartzite ridges' in ancient mountain chains. The red variety is often mistaken for Jasper but has a grainier texture under magnification.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its coarse, sugary texture on fresh breaks. It is commonly found in glacial till, riverbeds, and mountainous regions like the Appalachians or the Iron Range of the Midwest.
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