sedimentary

Chert (Jasper/Agate variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: tan, reddish-brown, and gray; Lustre: waxy to dull; Crystal structure: Trigonal/Microcrystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6 - 2.65

Hardness: 6
Color: tan, reddish-brown, and gray

Identified June 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the precipitation of silica-rich fluids within sedimentary rock cavities or by the accumulation of siliceous organisms like diatoms and radiolaria. Often found in limestone or as nodules in soil/landscaping rock.

Uses & applications

Historically used for stone tools and arrowheads due to its sharp edges when broken. Currently used for decorative landscaping, lapidary work (polishing), and as a gemstone (jasper/agate varieties).

Geological facts

This specimen appears to be a water-worn or weathered nodule. Because it is microcrystalline, it breaks with a conchoidal fracture, similar to glass, which is why it was the primary material for prehistoric toolmaking.

Field identification & locations

Identify in the field by its waxy texture, smooth conchoidal fractures, and hardness (it will scratch glass). Commonly found in stream beds, gravel pits, and landscaping mulch. This specific piece shows a mix of chalcedony and jasper-like coloration.