Meditation.
The practice of stilling the mind through focused attention, often paired with a stone held in the hand or placed nearby.
Meditation is the broad family of practices for training attention. The forms vary widely (breath awareness, mantra, open monitoring, loving-kindness, guided visualisation), but they share a common shape: a deliberate seat, a chosen anchor for the attention, and a willingness to keep coming back to that anchor when the mind wanders, which it always will.
In crystal practice, a stone often becomes part of the anchor. It might be held in the palm so its weight and temperature give the body something concrete to return to. It might be placed on the chest while lying down, on the brow during a longer session, or simply set within sight on a low table. The choice of stone is a matter of feel and association. Amethyst and clear quartz are common defaults, but a piece that someone returns to again and again will usually outperform a "correct" choice from a list.
A few minutes most days does more than an hour once a month. Meditation is one of the few practices where consistency is the whole game.