Rock crystal, compared to glass, which has an amorphous structure, shows a rhombohedral crystallization in the form of hexagonal prisms. In its pure state it is completely transparent, and if during crystallization it has incorporated other minerals, it takes on various tones: amethyst, agate, tiger’s eye, etc. Since ancient times they have been considered gems of great value. In various rituals it was used to concentrate on sunlight and thus ignite the sacred fire. It is not surprising that its beauty and properties have always generated attraction, especially due to its ability to disperse light with a spark that seems to arise from its interior, something very attractive. All this has translated into a rich symbolism, very extensive and characteristic of each people; for example, in a culture where there is aversion to material riches, negative meanings develop, while in others they are simple symbols of vanity, and in others, especially in the medieval era, it was attributed with magical properties of all kinds: cure diseases, antidote against poison, or as a talisman against evil spirits, as it was believed that a large crystal fell from Lucifer’s forehead when he descended into the hells. By the Renaissance it was a symbol of courage and character, or as recognition and reward for a certain state after a more or less difficult process. Today it is used as a talisman or in crystal therapy, and in jewelry. In this case, crystals are often heat-treated and with various additives to enhance their appearance. This, like many other symbols, has the property of concentrating the mind’s attention on a way of being and doing for each person. Currently, the crystallographic properties of this mineral cause it to resonate at a unique and stable frequency, making it useful as a time base in devices such as clocks; also, due to its ability to polarize light it is used in polarization microscopes and, because of its piezoelectric effect (ability to generate a small current when pressed), it ranges from a lighter to some types of microphones.