sedimentary
Chert (with Quartz Vein)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-green with white veins; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Grayish-green with white veins
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-green with white veins; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments. The white veins are later quartz infills in cracks caused by tectonic stress.
Uses & applications
Historically used for stone tools and flintknapping. Currently used as decorative river stones, in landscaping, or as tumbled collector and lapidary pieces.
Geological facts
Chert is one of the most durable sedimentary rocks. When it contains a cross or 'X' pattern of veins, it is sometimes referred to as a 'lucky stone' or 'cross stone' by beachcombers.
Field identification & locations
Identify by its waxy texture, smooth water-worn surface, and ability to scratch glass. Commonly found on beaches, riverbeds, and in limestone outcrops.
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