metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on the Mohs scale. Color: Tan, yellowish-orange, or white (due to iron oxide staining). Luster: Vitreous (glassy) to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.6-2.7.
- Hardness
- 7 on the Mohs scale
- Color
- Tan, yellowish-orange, or white (due to iron oxide staining)
- Luster
- Vitreous (glassy) to dull
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Physical properties
Hardness: 7 on the Mohs scale. Color: Tan, yellowish-orange, or white (due to iron oxide staining). Luster: Vitreous (glassy) to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. This specimen has been further shaped into a rounded pebble by high-energy water transport (fluvial or beach erosion), likely over thousands of years.
Uses & applications
Used industrially as a source of silica for glass making, in construction as crushed stone or railway ballast, and in decorative landscaping. Polished pebbles are often used in jewelry or as 'worry stones'.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, which is why it is frequently found as rounded pebbles on beaches or in riverbeds. While sandstone breaks around grains, quartzite breaks through the grains due to its interlocked crystalline structure.
Field identification & locations
Identify in the field by its hardness (it will scratch glass and steel) and its grainy but fused texture. It is commonly found on coastlines, in glacial till, and in eroded mountainous regions. This specific rounded shape indicates a history of water erosion.
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