metamorphic
Red Quartzite / Metasandstone River Pebble
Quartzite (primarily SiO2 with hematite inclusions)
Hardness: 7 (Mohs scale); Color: Reddish-brown to maroon; Luster: Dull to waxy; Structure: Granoblastic/Crystalline; Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Reddish-brown to maroon
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Reddish-brown to maroon; Luster: Dull to waxy; Structure: Granoblastic/Crystalline; Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure fused sand grains together, while iron oxides (hematite) provided the red coloration. This specimen has been further shaped by high-energy water transport (river or beach erosion).
Uses & applications
Commonly used as decorative garden stone, in construction aggregates, or as a source for silica. Smooth pebbles are popular for rock tumbling and as 'worry stones' for collectors.
Geological facts
Quartzite is so tough that it often outlasts the original mountains where it formed. When hit with a hammer, it will typically break across the quartz grains rather than around them, unlike its parent rock, sandstone.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife (H=5.5) and its smooth, water-worn texture. Commonly found in glaciated regions or riverbeds. Collectors look for unique vein patterns (as seen in this specimen) created by quartz-filled fractures.
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