metamorphic
Rounded quartz-rich pebble, possibly quartzite or granitic gneiss
Quartzite (mostly SiO₂) or quartz-rich granitoid; exact identification requires testing
AI-generated identification · may be incorrectGray-white, fine- to medium-grained, dull to slightly glassy luster, rounded by abrasion; quartz hardness is 7 Mohs, with no obvious cleavage. The rusty-brown surface may be iron-oxide staining or weathered feldspar/mica.
Identified More metamorphic →
Explore Rounded quartz-rich pebble, possibly quartzite or granitic gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Gray-white, fine- to medium-grained, dull to slightly glassy luster, rounded by abrasion; quartz hardness is 7 Mohs, with no obvious cleavage. The rusty-brown surface may be iron-oxide staining or weathered feldspar/mica.
Formation & geological history
Likely a glacially or stream-transported pebble eroded from quartzite, granite, or gneiss; its rounded shape reflects prolonged abrasion. The original rock may be Precambrian or younger, but age cannot be determined visually.
Uses & applications
Suitable mainly as a decorative stone, landscaping pebble, or teaching specimen; not gem-grade and unlikely to have commercial construction value as a single pebble.
Geological facts
Quartzite commonly resists weathering and accumulates in gravel beds, beaches, and glacial deposits. A streak test, hardness test, and inspection of fresh surfaces would distinguish it from granite or gneiss.
Field identification & locations
Common in gravel and shoreline deposits worldwide; scratch testing with a steel knife (quartz should resist) and examining grain boundaries with a loupe are useful field methods. Effervescence with dilute acid would suggest carbonate rock instead.
More like this
