Small grains tell how the rock cooled

Adão Mendes’s explainer for the Portuguese Association of Biology and Geology Teachers links granite’s granular texture with magma cooling slowly at depth. Its characteristic minerals include quartz and feldspars; micas may also be present. This general explanation encourages a closer look at stone, but recognising colours and grains is not enough to identify a sample’s origin.

If granite formed at depth, how do we see it in an outcrop? The British Geological Survey links its exposure to uplift, erosion and weathering over millions of years. Formation and exposure at the surface are different stages in its story.

It also helps to distinguish rock from mineral. In granite, different minerals occur together as interlocking crystals. Recognising that combination differs from observing a single mineral in isolation. Relative crystal sizes and their arrangement help describe texture; one colour does not tell the rock’s whole story.