sedimentary

Chert or silicified limestone fragment

Microcrystalline quartz (SiO₂), possibly calcareous chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 if chert, with dull to waxy luster, very fine grain, tan-gray color, and irregular conchoidal-looking fractures. The pale, earthy appearance could also indicate limestone or weathered silicification; crystal structure is microcrystalline rather than visibly crystalline.

Identified September 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed as silica replaced or cemented sedimentary material, potentially during burial diagenesis; exact age cannot be determined from the image. Common in sedimentary basins, river gravels, limestone formations, and exposed bedrock.

Uses & applications

Chert is used historically for fl tools and occasionally as aggregate or decorative stone; limestone is widely used for cement, lime, and construction. This small weathered fragment has little commercial value.

Geological facts

Chert commonly produces sharp edges when fractured and may occur in nodules or bedded layers. A steel file or knife should barely scratch true chert, while dilute hydrochloric acid fizzes strongly on calcite-rich limestone.

Field identification & locations

Look for a glassy or waxy fracture, lack of visible grains, and resistance to scratching; test acid only on an inconspicuous spot. Similar specimens occur worldwide, especially in flint-bearing chalks, limestones, and stream deposits.