igneous
Orbicular Granite
Orbicular Granidiorite / Plutonic Igneous Rock
Hardness: 6-7 (Mohs scale), Color: black, tan, and cream mottled/circular patterns, Luster: Vitreous to dull when unpolished, Crystal Structure: Phaneritic with orbicles, Cleavage: Imperfect, Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 6-7 (Mohs scale), Color: black, tan, and cream mottled/circular patterns, Luster: Vitreous to dull when unpolished, Crystal Structure: Phaneritic with orbicles, Cleavage: Imperfect, Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the cooling of magma deep underground where nucleated rhythmic growth of minerals (plagioclase, biotite, hornblende) occurs around a seed crystal or rock fragment during the crystallization process.
Uses & applications
Used primarily as decorative stones in jewelry, lapidary arts, high-end construction countertops, and as prized geological specimens for collectors.
Geological facts
Orbicular rocks are exceptionally rare; less than 1% of granite occurrences worldwide exhibit this specific orbicular texture, making them highly sought after by museums and private collectors.
Field identification & locations
Identify by looking for distinct circular or 'eye-like' mineral bands within a granitic matrix. Commonly found in specific localities like Western Australia, Chile, and parts of the United States (California/Idaho).
