metamorphic
Quartzite (Water-worn Pebble)
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-white to light pink; Luster: Vitreous (glassy) to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: ~2.65
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white to light pink
- Luster
- Vitreous (glassy) to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white to light pink; Luster: Vitreous (glassy) to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: ~2.65
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone subjected to extreme heat and pressure, causing quartz grains to recrystallize into a interlocking mosaic. This specific specimen has been further shaped and smoothed by fluvial or coastal water erosion.
Uses & applications
Used in construction as crushed stone, in railway ballast, and in the production of glass and industrial silica. High-quality specimens are used in lapidary work and garden landscaping.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges of mountain ranges because it resists weathering better than surrounding rocks. Unlike sandstone, when quartzite breaks, it fractures through the sand grains rather than around them.
Field identification & locations
Identify in the field by its hardness (it will easily scratch glass and stainless steel) and its crystalline appearance when freshly broken. Commonly found in riverbeds, glacial moraines, and ancient mountain belts. Collectors look for unique shapes like this 'heart-shaped' specimen.
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