mineral

Gray chalcedony (rough, possibly agate-grade)

Chalcedony, microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Gray to blue-gray, waxy to vitreous luster, with a massive microcrystalline structure and no visible cleavage; Mohs hardness 6.5–7, specific gravity about 2.6. The image shows a small, opaque-to-translucent rough piece with broken surfaces.

Identified October 14, 2026More mineral →

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Physical properties

Formation & geological history

Forms as silica-rich fluids deposit microscopic quartz in cavities and fractures, often in volcanic rocks. Such deposits occur across many geological ages; the specimen’s exact age and source cannot be determined from the photo.

Uses & applications

Used for beads, cabochons, carvings, and ornamental objects; common rough pieces are also collected.

Geological facts

Chalcedony is the fine-grained form of quartz; banded varieties are called agate, while uniformly colored varieties have other trade names.

Field identification & locations

Identify by its waxy appearance, hardness, and conchoidal fracture; it commonly occurs in volcanic cavities and sedimentary silica deposits worldwide. The photo does not show diagnostic banding, so a more specific identification is not supported.