igneous
Polished orbicular granite heart
Granite, commonly quartz–alkali feldspar–plagioclase–biotite granite; exact locality-dependent
AI-generated identification · may be incorrectHardness about 6–7 Mohs; gray-brown, coarse-grained, with reflective feldspar/quartz and dark biotite or hornblende. Interlocking crystals produce a granular texture; no dominant cleavage as a rock, though feldspar grains cleave.
Identified More igneous →
Explore Polished orbicular granite heart in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness about 6–7 Mohs; gray-brown, coarse-grained, with reflective feldspar/quartz and dark biotite or hornblende. Interlocking crystals produce a granular texture; no dominant cleavage as a rock, though feldspar grains cleave.
Formation & geological history
Slow cooling of silica-rich magma deep in the continental crust, generally Precambrian to Phanerozoic in age; later cut and polished into a heart. The strongly layered appearance may reflect gneissic banding or oriented mineral-rich zones rather than typical uniform granite.
Uses & applications
Used for decorative carvings, bookends, countertops, monuments, and mineral collections; limited jewelry use because of its coarse grain. Value is mainly ornamental and depends on size, polish, pattern, and locality.
Geological facts
Granite is an intrusive igneous rock whose crystals are visible because underground cooling is slow. The specimen’s rounded polish and display stand are human-made, but the material remains geological.
Field identification & locations
Identify it by visible interlocking quartz/feldspar crystals, dark mica or amphibole, substantial weight, and resistance to scratching with steel; a glassy surface alone is not diagnostic. Common worldwide, especially in continental shields and mountain belts.
