sedimentary

Banded Chert (Agate/Jasper blend)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Multi-colored bands (brown, white, grey, tan); Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.65.

Hardness: 6
Color: Multi-colored bands (brown, white, grey, tan)
Luster: Waxy to vitreous

Identified May 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in sedimentary environments. Banding occurs as silica concentrations vary over time, often within limestone or through secondary deposition in rock cavities.

Uses & applications

Used for making jewelry (cabochons), lapidary art, and historically used for stone tools due to its sharp conchoidal fracture. Also used as decorative gravel.

Geological facts

This specimen shows distinct banding similar to Lake Superior agates. Microcrystalline quartz varieties like this are exceptionally durable and can preserve detailed geological history within their layers.

Field identification & locations

Identify in the field by its waxy texture, inability to be scratched by a steel knife, and smooth, curved (conchoidal) fracture surfaces. Commonly found in riverbeds, glacial tills, and sedimentary outcrops.

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