igneous
Polished orbicular granite (likely larvikite-type stone)
Coarse-grained granitoid composed mainly of feldspar, quartz, and dark mafic minerals; exact variety is uncertain from the image
AI-generated identification · may be incorrectHardness about 6–7 Mohs; mottled cream, gray, black, and rusty-brown coloration with a granular texture and vitreous-to-dull luster. Interlocking crystals show no obvious cleavage on the polished surface; specific gravity is typically 2.6–2.8.
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Physical properties
Hardness about 6–7 Mohs; mottled cream, gray, black, and rusty-brown coloration with a granular texture and vitreous-to-dull luster. Interlocking crystals show no obvious cleavage on the polished surface; specific gravity is typically 2.6–2.8.
Formation & geological history
A slowly cooled intrusive igneous rock formed when magma crystallized deep in the crust, probably during a Precambrian or Paleozoic plutonic event. The rounded shape and shine result from human polishing and abrasion.
Uses & applications
Used as a decorative stone, paperweight, cabochon, or lapidary specimen; similar granitoids are used for countertops, monuments, tiles, and aggregate. Common polished pieces generally have modest collector value.
Geological facts
The black-and-white pattern reflects contrasting feldspar and mafic mineral concentrations, while rusty areas likely represent weathered iron-bearing minerals. It may be sold under informal trade names such as “black-and-white granite” or “orbicular granite.”
Field identification & locations
Commonly sourced from granite-producing regions worldwide, including Scandinavia, India, Brazil, and Madagascar. Identify it by its coarse interlocking crystals, feldspar-rich pale areas, dark biotite/amphibole, and granite-like density; a fresh unpolished surface or thin section is needed for precise classification.
