Polished white chalcedony or milky quartz pebble

White to cream, opaque to slightly translucent, with a smooth polished surface and a brown internal vein or inclusion. Quartz-family hardness is approximately 6.5–7 on the Mohs scale; vitreous to waxy luster; trigonal quartz structure, although individual crystals are generally too fine to see in chalcedony. No obvious cleavage; conchoidal fracture. The rounded shape indicates tumbling, natural abrasion, or deliberate shaping. Exact identification cannot be confirmed from the photograph alone.

Most likely formed when silica-rich groundwater deposited quartz or chalcedony in cavities, fractures, or vesicles in volcanic or sedimentary rock. The brown marking may be iron oxide or hydroxide such as limonite or goethite. Quartz deposits range from Precambrian to recent, so a precise geological age cannot be determined from the image. The present rounded form is probably human-polished or naturally water-worn.

Used for ornamental stones, beads, cabochons, carvings, paperweights, and inexpensive jewelry. Quartz and chalcedony are also important industrial silica materials, although this small polished specimen has primarily decorative or collecting value.

White chalcedony and milky quartz are visually similar. Chalcedony is made of extremely fine interlocking quartz fibers, while milky quartz consists of larger quartz crystals containing microscopic fluid inclusions or defects. Brown seams commonly result from iron-bearing fluids moving through fractures. The nearly spherical shape and uniformly smooth surface strongly suggest tumbling.

Commonly found as pebbles and cavity fillings in volcanic regions, hydrothermal veins, weathered silica-rich rocks, and river gravels. Field identification can be supported by a hardness test: genuine quartz should scratch ordinary glass but should not be scratched by a steel knife. It should not fizz in dilute hydrochloric acid. A strong flashlight may reveal slight translucency around the edges. A specific-gravity test, close-up examination, and testing of an inconspicuous area would help distinguish it from howlite, calcite, ceramic, or glass. The image alone does not rule out a manufactured glass or ceramic bead, but its appearance is consistent with a polished quartz-family specimen.