igneous
Weathered granitic or gneissic pebble
Granite–gneiss assemblage; quartz + feldspar + dark mafic minerals
AI-generated identification · may be incorrectHardness approximately 6–7 Mohs; gray-green, mottled, fine-to-medium grained, with a dull to slightly vitreous luster. The irregular light-and-dark banding suggests altered or foliated feldspar- and quartz-rich rock rather than a single crystal mineral.
Identified More igneous →
Explore Weathered granitic or gneissic pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness approximately 6–7 Mohs; gray-green, mottled, fine-to-medium grained, with a dull to slightly vitreous luster. The irregular light-and-dark banding suggests altered or foliated feldspar- and quartz-rich rock rather than a single crystal mineral.
Formation & geological history
Likely formed from slowly cooled felsic magma and later metamorphic deformation, potentially billions of years old depending on locality; its rounded shape reflects erosion and transport. Exact identification requires a fresh surface, hardness testing, and mineral examination.
Uses & applications
Common granite and gneiss are used as construction stone, aggregate, paving, monuments, and decorative material; this small specimen has mainly educational or modest collecting value.
Geological facts
The pale portions are probably quartz and feldspar, while darker areas may contain biotite, amphibole, or chlorite. Weathering can produce the greenish-gray coloration and obscure the original texture.
Field identification & locations
Look for visible interlocking grains, quartz’s lack of cleavage, feldspar cleavage, and possible foliation; it should scratch glass but not be scratched by a steel knife. Common in continental shields, mountain belts, glacial deposits, and stream gravels.
