Before there were geologists, there were stonecutters. And before we understood granite (to the extent that we do understand granite), those guys had been quarrying it out of the ground for centuries. In working a granite quarry and making useful items like curbstones and building blocks and cobblestones and ashlars, quarriers needed to figure out the stone's rift, grain and hardway. My new article explains what those are.
Granite curbs, cleaved on the grain and finished on the rift Geology Guide photo