mineral

Blue-gray chalcedony (likely agate/jasper fragment)

Microcrystalline quartz, SiO₂ (chalcedony)

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; blue-gray, translucent to opaque, with a waxy to vitreous luster and irregular conchoidal fracture. The pale brown outer rind may be weathered host rock or iron staining; visible white veining is likely quartz.

Identified September 21, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities, fractures, or volcanic vesicles and crystallizes as microcrystalline quartz, commonly during volcanic activity and later weathering. Exact age and locality cannot be determined from the image.

Uses & applications

Used for beads, cabochons, carvings, polished specimens, and ornamental stone; large uniform pieces may be used as agate or jasper material.

Geological facts

Chalcedony is a quartz variety composed of extremely fine intergrowths of quartz polymorphs. Blue-gray coloration can result from microscopic inclusions, scattering, or trace minerals.

Field identification & locations

Common in volcanic terrains, river gravels, and weathered basalt, especially in Brazil, Uruguay, Mexico, India, and the western United States. A glassy appearance, waxy luster, lack of obvious cleavage, and ability to scratch glass support identification; acid does not react.