Rock IdentifierGranite
Key takeaways
- Granite is a coarse-grained igneous rock of quartz, feldspar, and mica.
- Its visible, interlocking crystals mean it cooled slowly deep underground.
- The 'granite' sold for countertops is a commercial term covering several rock types.
What it is
Granite is the textbook intrusive igneous rock: molten magma that cooled slowly kilometers underground, giving crystals time to grow large enough to see. It's typically light-colored and speckled, and it makes up much of the continental crust. Because it's a rock, not a mineral, it has no single formula — it's a mixture.
Reading the grains
Look closely and you can name the ingredients: glassy grey quartz, blocky white-to-pink feldspar (usually the most abundant), and flecks of shiny black or silvery mica. Sometimes dark amphibole needles appear too. The interlocking, randomly oriented crystals with no layering mark it as igneous rather than sedimentary or metamorphic.
Look-alikes & the countertop caveat
Gneiss can look similar but shows aligned mineral bands (foliation) from metamorphism, whereas granite's grains are random. In the stone trade, 'granite' is used loosely for many hard speckled rocks — including some that a geologist would call gabbro or gneiss — so a countertop label isn't a precise identification.
