Tumbled quartz-rich rock, likely quartzite or milky quartz with iron-oxide staining

Rounded and polished/tumbled specimen with a pale gray to creamy-white body, translucent milky quartz areas, and irregular reddish-brown to dark brown iron-oxide veins or stains. Quartz has a Mohs hardness of 7, vitreous to waxy luster, no cleavage, conchoidal fracture, and specific gravity around 2.65. The visible grainy texture suggests quartzite rather than a single quartz crystal, though the photograph is not sufficient for certainty.

If quartzite, it formed when quartz-rich sandstone was subjected to heat and pressure during metamorphism, commonly during mountain-building events. Iron-bearing groundwater or hydrothermal fluids later produced hematite/goethite staining and veining. The specimen is likely geologically ancient, potentially Paleozoic or older depending on its source region, but its exact age cannot be determined from the image.

Most likely a decorative or lapidary specimen used for collecting, tumbling, cabochons, and ornamental stone. Quartzite is also widely used as crushed stone, aggregate, paving, countertops, and building stone when available in large sound blocks. This particular rounded piece appears primarily collectible rather than industrial.

The brown coloration is probably iron-oxide alteration rather than the primary color of the quartz. Quartzite commonly resembles massive quartz but generally shows a fused, granular texture and breaks across grains rather than around loose sandstone grains. A specimen may also be classified simply as iron-stained milky quartz if it lacks clear metamorphic texture.

Commonly found in metamorphic mountain belts and in stream or glacial gravels derived from quartzite outcrops. In the field, test a fresh surface: quartz-rich quartzite should scratch ordinary glass and resist scratching by a steel knife. It should not fizz with dilute hydrochloric acid unless carbonate minerals are present. Look for interlocking quartz grains, very high hardness, lack of obvious cleavage, and reddish-brown hematite/goethite along fractures. Exact identification would benefit from a fresh fracture, streak, acid test, and possibly thin-section or chemical analysis.