igneous
Rounded granitic/gneissic cobble
Probable granodiorite or orthogneiss; quartz–feldspar–biotite aggregate
AI-generated identification · may be incorrectMedium-gray, speckled, fine-to-medium grained, with weak foliation or compositional banding and a dull-to-slightly sparkly luster. Likely Mohs hardness 6–7; massive to weakly gneissic, with no obvious cleavage; specific gravity about 2.65–2.75.
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Physical properties
Medium-gray, speckled, fine-to-medium grained, with weak foliation or compositional banding and a dull-to-slightly sparkly luster. Likely Mohs hardness 6–7; massive to weakly gneissic, with no obvious cleavage; specific gravity about 2.65–2.75.
Formation & geological history
Probably an alluvial or glacially transported cobble rounded by abrasion. The rock itself likely formed deep in the crust during Precambrian to Paleozoic plutonic/metamorphic events; its exact age cannot be determined from the photograph.
Uses & applications
Commonly used as landscaping stone, aggregate, paving material, and garden cobbles; generally has little gemstone or collector value.
Geological facts
The granular texture suggests interlocking quartz and feldspar with dark mica or amphibole. The rounded shape reflects transport rather than original rock formation.
Field identification & locations
The Belgrade-area regional setting favors transported metamorphic and igneous cobbles derived from broader Balkan crust, though a precise source is impossible visually. A fresh broken surface, acid test, and hand lens would help distinguish granodiorite from gneiss; visible alignment of dark minerals supports gneiss.
