A luminous layer provides a long-term lightning effect in the dark. It requires only a short-term exposure to light. Usually the pointers, and sometimes the hour markers are coated with this. This, very durable, mineral crystal has improved protection. Tough, durable and elegant; a bracelet made of stainless steel gives the watch a classic quality look. A battery-powered quartz watch is controlled by fluctuations in a crystal of the mineral quartz. These oscillations change very little over time, which is why quartz is often used - because it retains its accuracy.