sedimentary
Chert (Hagstone / Lucky Stone)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Tan, beige, grey; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); High durability.
- Hardness
- 6
- Color
- Tan, beige, grey
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Tan, beige, grey; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); High durability.
Formation & geological history
Formed as a chemical precipitate or through the replacement of limestone. This specific specimen shows extensive water erosion and boring by marine organisms or pebbles, creating a 'Hagstone' structure.
Uses & applications
Used historically for tools and weapons; currently used for decorative purposes, aquarium decor, and as 'lucky charms' in folklore.
Geological facts
Rocks with natural holes, known as hagstones, were historically believed to ward off nightmares and bad luck. They are common in coastal areas where wave action accelerates erosion.
Field identification & locations
Identify by its hardness (will scratch glass) and smooth, weathered surface. Holes are naturally bored by piddock clams or abrasive sand and water action. Found on gravel beaches globally.
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