The mountain crystal and its colorful varieties appear in a multi-crystalline form, in the form of clearly shaped crystals – hexagonal columns with a diameter up to 8 meters and a weight of many tons. Quartz varieties included in the group have a completely different structure chalcedony.

They are so different from rock crystal or amethyst, that for many centuries they were considered a separate mineral. Meanwhile, they have the same chemical composition and, like quartz, crystallize in a trigonal system. The main difference is this, that chalcedony, similarly to the usual methods obtained technical metals, has a cryptocrystalline structure or otherwise – microcrystalline. Even the smallest piece of chalcedony consists of thousands or hundreds of thousands of tiny crystals.

This difference is mainly due to the crystallization conditions. Large quartz crystals, just like large crystals of other minerals, and also metals, they can only arise under conditions of very slow and steady crystallization. For metals and minerals crystallizing from alloys, the main condition will be a very slow temperature drop. For minerals crystallizing from solutions - a very slow flow of the elements forming the crystal in the solution. An equally important condition, and this is for both crystallization processes, is the purity of the alloy or solution. Each impurity can become a nucleus for crystal formation. The more pollution, the more crystals are born at the same time and the finer-grained structure the crystalline body will have. The ideal conditions are then, when pollution, potential nuclei of crystallization, there is little, and the crystallization process is very slow. Under such conditions, there cannot be a simultaneous one, starting at the same moment of "birth” a few crystals, and when the first crystal begins to grow, it becomes impossible to give birth to another one on another nucleus of crystallization. The former seemed to attract all the atoms it needed to grow, ions or molecules.