sedimentary
Banded Chert (Wonderstone-style)
Silicon Dioxide (SiO2)
Hardness: 6.5-7.0 (Mohs). Color: Cream, tan, and reddish-brown bands. Luster: Waxy to dull. Crystal Structure: Microcrystalline/Cryptocrystalline. Cleavage: None, exhibits conchoidal fracture.
- Hardness
- 6
- Color
- Cream, tan, and reddish-brown bands
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7.0 (Mohs). Color: Cream, tan, and reddish-brown bands. Luster: Waxy to dull. Crystal Structure: Microcrystalline/Cryptocrystalline. Cleavage: None, exhibits conchoidal fracture.
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation from groundwater within sedimentary layers. The banding often results from rhythmic deposition or iron oxide staining during diagenesis.
Uses & applications
Used primarily for lapidary work, decorative cabochons, and as collectable 'landscape' stones. Historically used for stone tools due to its sharp fracture edges.
Geological facts
This specific aesthetic, often called 'Wonderstone' when it occurs in volcanic tuffs or 'Banded Chert', is prized for its resemblance to desert landscapes. It is chemically identical to quartz but has a structure so fine that individual crystals cannot be seen under a standard microscope.
Field identification & locations
Can be identified by its smooth, shell-like fracture pattern and the fact that it will scratch glass. Look for it in sedimentary outcrops or as river-worn nodules in gravel beds.
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