sedimentary

Likely chert or flint

Microcrystalline quartz (SiO₂), commonly called chert; exact identification requires testing

AI-generated identification · may be incorrect

Dark purplish-brown, dull to waxy luster, very fine-grained and massive, with irregular conchoidal-looking fracture and no visible cleavage. Hardness about 6.5–7 Mohs; specific gravity approximately 2.6.

Identified August 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms by silica-rich replacement or accumulation of microscopic quartz in sedimentary rocks, often in limestone or chalk. It may range from Paleozoic to recent in age, depending on its host formation.

Uses & applications

Used historically for sharp-edged tools, arrowheads, and fire-starting; today mainly a collector specimen, aggregate, and occasional dimension-stone material.

Geological facts

Its edges can be extremely sharp when fractured. Purple coloration may result from iron, manganese, organic matter, or surface weathering; the specimen could also be a weathered jasper-like silica rock.

Field identification & locations

Common in limestone regions, river gravels, and glacial deposits. Confirm by attempting to scratch glass and inspecting for a smooth conchoidal fracture; it should not fizz in dilute hydrochloric acid unless coated with carbonate.