Crystals vibrate at their own frequency much like the cells in your body. These vibrations can be felt by many. Crystals have a Piezoelectric effect whereby they create electricity. This is why crystals are essential elements in microphones, quartz watches, lasers, computer and more.
Crystals are beleived to have health benefits for the body, mind and soul. Allowing yourself to be "guided" or drawn to the crystal that is best for you is sometimes an affirming experience. Many people find that they intuitively will pick a stone that meets a need they have at the time. This supports the belief that crystals have a vibration that we can naturally connet with on some higher level.
In the context of this topic, spirituality is the thought or feeling that we are connected to a higher source or vibration. It is not an assignment or subscription of belief in one system. Cyrstals are used by many to support a connection to a higher level where a sense of well being, love and unity with a deeper meaning can be achieved.