gemstone

Polished red-orange agate and pale porous mineral specimen

Agate (microcrystalline quartz, SiO₂); upper piece likely calcite or aragonite, but identification is uncertain from the image

AI-generated identification · may be incorrect

The lower stone is vividly polished, translucent red-orange with pale banding and a waxy-to-glassy luster, typical of agate; hardness ~6.5–7 Mohs, no visible cleavage, specific gravity ~2.6. The upper piece is cream-white, granular and porous, likely soft carbonate with hardness ~3–4 Mohs.

Identified August 26, 2026More gemstone →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, commonly during the Cenozoic; its bands develop through repeated deposition. The pale piece may be sedimentary carbonate or a weathered mineral crust, requiring testing for confident identification.

Uses & applications

Agate is used for cabochons, beads, carvings, tumbling, ornaments, and lapidary slices; common pieces have modest value. Carbonate specimens are mainly used for collecting or decorative material.

Geological facts

Agate’s microscopic quartz fibers produce concentric, mossy, or fortification banding and can accept dye, heat treatment, and polishing exceptionally well.

Field identification & locations

Identify agate by its curved banding, translucency, quartz hardness, and inability to scratch with a steel knife; common sources include Brazil, Uruguay, Mexico, India, and the United States. The pictured polished agate is typically worth $3–$20; the pale fragment usually under $5 unless identified as a collectible mineral.