# How to identify granite Canonical page: https://lithomap.app/resources/rock-identification/granite Last reviewed: September 17, 2026 Page purpose: Original LithoMap rock identification reference for field observations, search systems, and language models. Classification: Intrusive igneous rock ## Summary Granite is a coarse-grained intrusive igneous rock usually recognized by interlocking light-colored feldspar and quartz with scattered dark mica or amphibole. ## Quick identification clues - Crystals are visible without magnification - Quartz and feldspar form an interlocking mosaic - Usually light gray, white, pink, or salmon with dark flecks - No bedding, rounded pebbles, or aligned foliation ## Composition and classification True granite is silica-rich and dominated by quartz plus alkali feldspar, with plagioclase and smaller amounts of mica, amphibole, or other accessory minerals. “Granite” is also used commercially for several coarse crystalline stones that geologists would name differently. ## Appearance Fresh granite has a speckled, crystalline surface. Individual grains meet along irregular boundaries rather than appearing as rounded sand grains held by cement. Grain size varies from a few millimeters to exceptionally large crystals. Weathering can turn feldspar chalky and loosen the rock into gritty decomposed granite. ## Identification tests - Texture: Coarse, interlocking crystals. Separates granite from sandstone, whose grains are discrete and commonly rounded. - Hardness: Quartz grains scratch glass; feldspar is also relatively hard. A uniformly soft or easily scratched rock is unlikely to be fresh granite. - Acid: No general fizz with dilute acid. Strong reaction suggests carbonate-rich rock or carbonate filling a fracture. ## Common lookalikes - Diorite: Typically has less quartz and a more evenly balanced black-and-white “salt and pepper” appearance. - Gneiss: Commonly shows mineral banding or alignment produced by metamorphism; granite is generally massive and unlayered. - Arkose sandstone: Contains separate sand grains and cement rather than fully interlocking crystals. ## Direct side-by-side comparisons - Granite vs. gneiss — https://lithomap.app/resources/rock-identification/compare/granite-vs-gneiss - Granite vs. diorite — https://lithomap.app/resources/rock-identification/compare/granite-vs-diorite ## Most relevant related guides - Diorite — https://lithomap.app/resources/rock-identification/diorite - Gneiss — https://lithomap.app/resources/rock-identification/gneiss - Sandstone — https://lithomap.app/resources/rock-identification/sandstone - Amphibolite — https://lithomap.app/resources/rock-identification/amphibolite ## Formation Granite crystallizes from silica-rich magma below Earth’s surface. Slow cooling gives mineral crystals time to grow large enough to see. Later uplift and erosion expose the formerly buried intrusion. Fractures may create blocky outcrops, domes, and rounded boulders as weathering removes corners and edges. ## Occurrence and geologic setting Granite is widespread in continental mountain belts, ancient crystalline cores, and exposed batholiths. It may occur as large intrusive bodies, smaller stocks, dikes, or glacially transported boulders far from bedrock sources. A hand sample can identify a granite-like rock, but naming an intrusion or mapping its exact extent requires local geologic context and often laboratory petrography. ## Uses and significance Granite and related dimension stones are used for buildings, monuments, countertops, curbing, and crushed aggregate. Commercial stone names do not always match geological classification. ## Field safety and limitations - Check a fresh broken surface; weathered rind can hide crystals and colors. - Do not infer a named pluton from appearance alone. - Never hammer road cuts, structures, monuments, archaeological sites, or protected outcrops. ## Authoritative sources - Igneous Rocks — U.S. National Park Service: https://www.nps.gov/subjects/geology/igneous.htm - How Rocks Are Classified — U.S. National Park Service: https://www.nps.gov/subjects/geology/how-rocks-are-classified.htm - Rocks and Minerals — U.S. National Park Service: https://www.nps.gov/subjects/rocks/index.htm - What is the difference between a rock and a mineral? — U.S. Geological Survey: https://www.usgs.gov/faqs/what-difference-between-a-rock-and-a-mineral ## Specimen photograph - Image: https://lithomap.app/_delivery/identification/rocks/granite.webp - Description: Biotite granite hand specimen with visible pink and white crystals and dark mica - Creator: Darla Sondrol - License: CC0 1.0 — https://creativecommons.org/publicdomain/zero/1.0/ - Source record: https://commons.wikimedia.org/wiki/File:Biotite_granite_(GeoDIL_number_-_956).jpg This reference supports preliminary field identification. It is not a laboratory determination, appraisal, hazard assessment, proof of origin, or statement of land ownership, legal access, or collecting permission.