Different locations use different materials. I've seen small pea-stone, I've seen actual chipped granite. Sometimes I swear they brush it after application to bring up the nap. My home county used to spray the oil and then just dump stone everywhere and let the cars work it in. That was a nightmare for road bikes. Now that stone is getting more expensive, they've taken to doing it right: spray, spread, roll, then spray a top-coat. I've never crashed on chip-seal and I hope I never do -- it would cause deep lacerations instead of just a little rug burn. I can't believe any cyclist likes it, compared to smooth asphalt it costs around 2 mph in either speed or effort.