igneous
Polished orbicular granite (likely larvikite or orbicular diorite)
Quartz/feldspar-bearing granitoid with dark amphibole–biotite minerals; exact variety requires testing
AI-generated identification · may be incorrectCoarse crystalline, black-and-cream mottled pattern with orbicular/flow textures; vitreous to pearly luster. Hardness approximately 6–7 Mohs, non-cleaving overall, and relatively dense (about 2.7–3.0 g/cm³).
Identified More igneous →
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Physical properties
Coarse crystalline, black-and-cream mottled pattern with orbicular/flow textures; vitreous to pearly luster. Hardness approximately 6–7 Mohs, non-cleaving overall, and relatively dense (about 2.7–3.0 g/cm³).
Formation & geological history
A slowly cooled intrusive igneous rock formed when felsic to intermediate magma crystallized deep underground; orbicular textures developed through unusual crystallization around mineral nuclei. Typically Paleozoic to Precambrian in age, depending on locality.
Uses & applications
Used as a polished decorative stone, cabochon, sphere, or curio; related granitoids are used for countertops, monuments, flooring, and aggregate. Collector value is mainly aesthetic and workmanship-based.
Geological facts
The rounded shape is human-polished, while the intricate black-and-white pattern is natural mineral banding or orbicules rather than a fossil. The visible cavity or inclusion may contain altered feldspar, quartz, or mafic minerals.
Field identification & locations
Identify by its interlocking crystalline texture, lack of sedimentary layering, high hardness, and resistance to scratching; a streak test is usually white or colorless. Common sources include Norway, Madagascar, India, and other granite provinces.
