metamorphic
Quartzite with Iron Inclusions
Quartzite (SiO2) with Hematite/Limonite
Hardness: 7 (Mohs scale); Color: Rusty brown, reddish-orange, and grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Rusty brown, reddish-orange, and grayish-white
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Rusty brown, reddish-orange, and grayish-white; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure (metamorphism). The iron-rich coloration (red/brown) comes from the oxidation of iron minerals or groundwater staining within the pores of the original rock.
Uses & applications
Commonly used as crushed stone in road construction, as decorative landscaping stone, and occasionally in lapidary work for cabochons if the pattern is unique.
Geological facts
Quartzite is so tough that it often survives intense erosion better than the surrounding rocks, frequently forming the tops of ridges and mountains. It is harder than steel and will scratch a glass plate easily.
Field identification & locations
Field identification involves checking for hardness (it should scratch glass) and a sugary, grainy texture on broken surfaces. It is found globally in mountainous regions or ancient shield areas. For collectors, look for the 'conchoidal' fracture patterns on the edges.
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