metamorphic
Quartzite with Vugs
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: white to light tan with brown iron-stained pits; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none, conchoidal fracture; Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- white to light tan with brown iron-stained pits
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: white to light tan with brown iron-stained pits; Luster: vitreous to dull; Crystal structure: trigonal (microcrystalline); Cleavage: none, conchoidal fracture; Specific gravity: 2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure caused the recrystallization of sand grains. The holes (vugs) likely formed from the weathering or leaching out of more soluble minerals like calcite or fossils during transport in water.
Uses & applications
Primarily used in construction for road ballast, roofing granules, and as a decorative stone in landscaping or lapidary work.
Geological facts
Quartzite is so strong that when it breaks, it fractures through the sand grains rather than around them, unlike its parent rock sandstone. This specimen shows significant rounding, indicating it was moved by a river or waves.
Field identification & locations
Identify in the field by its extreme hardness (it will scratch glass) and lack of reaction to acid. Often found as rounded river pebbles or cobbles in glacial till or along high-energy beaches.
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